diff --git a/src/main/java/com/chat/liveon/auth/entity/Person.java b/src/main/java/com/chat/liveon/auth/entity/Person.java
index 3205be3..f49a9dc 100644
--- a/src/main/java/com/chat/liveon/auth/entity/Person.java
+++ b/src/main/java/com/chat/liveon/auth/entity/Person.java
@@ -1,15 +1,12 @@
 package com.chat.liveon.auth.entity;
 
-import com.chat.liveon.chat.entity.ChatMessage;
 import com.chat.liveon.chat.entity.ChatRoom;
 import jakarta.persistence.*;
-import lombok.AllArgsConstructor;
-import lombok.Builder;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
 
 @Entity
 @Getter
@@ -24,6 +21,9 @@ public class Person {
     private Role role;
     private String profilePicture;
 
+    @ManyToMany(mappedBy = "participants")
+    private Set<ChatRoom> chatRooms = new HashSet<>();
+
     public Person(String personId, String personName, String encodedPassword, Role role, String profilePicture) {
         this.personId = personId;
         this.personName = personName;
diff --git a/src/main/java/com/chat/liveon/auth/service/AuthService.java b/src/main/java/com/chat/liveon/auth/service/AuthService.java
index 4fc514e..a85b8b6 100644
--- a/src/main/java/com/chat/liveon/auth/service/AuthService.java
+++ b/src/main/java/com/chat/liveon/auth/service/AuthService.java
@@ -7,11 +7,11 @@
 import com.chat.liveon.auth.entity.Role;
 import com.chat.liveon.auth.exception.AuthenticationFailureException;
 import com.chat.liveon.auth.repository.PersonRepository;
+import com.chat.liveon.chat.service.ChatRoomService;
 import jakarta.servlet.http.Cookie;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import jakarta.servlet.http.HttpSession;
-import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -22,10 +22,12 @@
 public class AuthService {
     private final PasswordEncoder passwordEncoder;
     private final PersonRepository personRepository;
+    private final ChatRoomService chatRoomService;
 
-    public AuthService(final PasswordEncoder passwordEncoder, final PersonRepository personRepository) {
+    public AuthService(final PasswordEncoder passwordEncoder, final PersonRepository personRepository, ChatRoomService chatRoomService) {
         this.passwordEncoder = passwordEncoder;
         this.personRepository = personRepository;
+        this.chatRoomService = chatRoomService;
     }
 
     @Transactional
@@ -36,6 +38,7 @@ public void register(RegisterRequest authRequest) {
         String encodedPassword = passwordEncoder.encrypt(authRequest.personId(), authRequest.personPassword());
         Person person = new Person(authRequest.personId(), authRequest.personName(), encodedPassword, Role.ROLE_USER, authRequest.profilePicture());
         personRepository.save(person);
+        chatRoomService.addUserToAllChatRooms(person);
     }
 
     @Transactional
diff --git a/src/main/java/com/chat/liveon/auth/service/PasswordEncoder.java b/src/main/java/com/chat/liveon/auth/service/PasswordEncoder.java
index 7901d98..be5efbb 100644
--- a/src/main/java/com/chat/liveon/auth/service/PasswordEncoder.java
+++ b/src/main/java/com/chat/liveon/auth/service/PasswordEncoder.java
@@ -10,11 +10,8 @@
 import java.security.NoSuchAlgorithmException;
 import java.security.spec.InvalidKeySpecException;
 import java.security.spec.KeySpec;
-import java.util.Arrays;
 import java.util.Base64;
 
-import static java.util.Objects.hash;
-
 @Component
 public class PasswordEncoder {
 
diff --git a/src/main/java/com/chat/liveon/auth/service/PersonService.java b/src/main/java/com/chat/liveon/auth/service/PersonService.java
index 232ff90..4933242 100644
--- a/src/main/java/com/chat/liveon/auth/service/PersonService.java
+++ b/src/main/java/com/chat/liveon/auth/service/PersonService.java
@@ -1,4 +1,19 @@
 package com.chat.liveon.auth.service;
 
+import com.chat.liveon.auth.entity.Person;
+import com.chat.liveon.auth.repository.PersonRepository;
+import com.chat.liveon.chat.service.ChatRoomService;
+import org.springframework.stereotype.Service;
+
+@Service
 public class PersonService {
+    private final PersonRepository personRepository;
+
+    public PersonService(PersonRepository personRepository) {
+        this.personRepository = personRepository;
+    }
+
+    public Person findByPersonId(Long personId) {
+        return personRepository.findById(personId).orElseThrow();
+    }
 }
diff --git a/src/main/java/com/chat/liveon/chat/controller/ChatMessageController.java b/src/main/java/com/chat/liveon/chat/controller/ChatMessageController.java
index 6d0e9d7..3d8a0be 100644
--- a/src/main/java/com/chat/liveon/chat/controller/ChatMessageController.java
+++ b/src/main/java/com/chat/liveon/chat/controller/ChatMessageController.java
@@ -10,10 +10,7 @@
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.handler.annotation.SendTo;
 import org.springframework.stereotype.Controller;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.PathVariable;
-import org.springframework.web.bind.annotation.RequestMapping;
-import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.*;
 
 import java.util.List;
 
@@ -28,6 +25,7 @@ public class ChatMessageController {
     @SendTo("/topic/chatroom/{roomId}")
     public ChatMessageResponse sendMessage(@DestinationVariable("roomId") String roomId, ChatMessageRequest message) {
         Long roomIdLong = Long.parseLong(roomId);
+
         return chatMessageService.sendMessage(roomIdLong, message);
     }
 
@@ -35,6 +33,7 @@ public ChatMessageResponse sendMessage(@DestinationVariable("roomId") String roo
     @GetMapping("/chat-room/{roomId}/messages")
     public ResponseEntity<List<ChatMessageResponse>> getChatMessages(@PathVariable("roomId") Long roomId, @RequestParam(name = "page", defaultValue = "0") int page, @RequestParam(name = "size", defaultValue = "20") int size) {
         List<ChatMessageResponse> messages = chatMessageService.getMessagesByRoomId(roomId, page, size);
+
         return ResponseEntity.ok(messages);
     }
 }
diff --git a/src/main/java/com/chat/liveon/chat/controller/ChatMessageStatusController.java b/src/main/java/com/chat/liveon/chat/controller/ChatMessageStatusController.java
index c94d2d3..edb27f8 100644
--- a/src/main/java/com/chat/liveon/chat/controller/ChatMessageStatusController.java
+++ b/src/main/java/com/chat/liveon/chat/controller/ChatMessageStatusController.java
@@ -1,4 +1,33 @@
 package com.chat.liveon.chat.controller;
 
+import com.chat.liveon.chat.dto.response.UnreadMessagesResponse;
+import com.chat.liveon.chat.service.ChatMessageStatusService;
+import jakarta.servlet.http.HttpSession;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/api")
+@RequiredArgsConstructor
 public class ChatMessageStatusController {
+    private final ChatMessageStatusService chatMessageStatusService;
+
+    @PostMapping("/chat-room/{chatRoomId}/read-messages")
+    public ResponseEntity<Void> markMessagesAsRead(@PathVariable("chatRoomId") Long chatRoomId, HttpSession session) {
+        String personId = (String) session.getAttribute("personId");
+        chatMessageStatusService.markMessagesAsRead(chatRoomId, personId);
+
+        return ResponseEntity.ok().build();
+    }
+
+    @GetMapping("/chat-room/unread-messages")
+    public ResponseEntity<List<UnreadMessagesResponse>> getUnreadMessages(HttpSession session) {
+        String personId = (String) session.getAttribute("personId");
+        List<UnreadMessagesResponse> response = chatMessageStatusService.getUnreadMessages(personId);
+
+        return ResponseEntity.ok(response);
+    }
 }
diff --git a/src/main/java/com/chat/liveon/chat/controller/ChatRoomController.java b/src/main/java/com/chat/liveon/chat/controller/ChatRoomController.java
index 19fd108..247e77b 100644
--- a/src/main/java/com/chat/liveon/chat/controller/ChatRoomController.java
+++ b/src/main/java/com/chat/liveon/chat/controller/ChatRoomController.java
@@ -3,6 +3,7 @@
 import com.chat.liveon.chat.dto.request.ChatRoomRequest;
 import com.chat.liveon.chat.dto.response.AllChatRoomResponse;
 import com.chat.liveon.chat.dto.response.ChatRoomResponse;
+import com.chat.liveon.chat.service.ChatMessageStatusService;
 import com.chat.liveon.chat.service.ChatRoomService;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
@@ -20,6 +21,7 @@
 public class ChatRoomController {
 
     private final ChatRoomService chatRoomService;
+    private final ChatMessageStatusService chatMessageStatusService;
 
     @Operation(summary = "채팅방 생성 API")
     @PostMapping("/chat-room")
@@ -32,8 +34,17 @@ public ResponseEntity<ChatRoomResponse> createChatRoom(@RequestBody ChatRoomRequ
 
     @Operation(summary = "채팅방 조회 API")
     @GetMapping("/chat-room")
-    public ResponseEntity<List<AllChatRoomResponse>> getChatRoom() {
-        List<AllChatRoomResponse> response = chatRoomService.getAllChatRoom();
+    public ResponseEntity<List<AllChatRoomResponse>> getChatRoom(HttpSession session) {
+        String personId = (String) session.getAttribute("personId");
+        List<AllChatRoomResponse> response = chatRoomService.getAllChatRoom(personId);
         return ResponseEntity.ok(response);
     }
+
+    @PostMapping("/chat-room/{chatRoomId}/enter")
+    public ResponseEntity<Void> enterChatRoom(@PathVariable("chatRoomId") Long chatRoomId, HttpSession session) {
+        String personId = (String) session.getAttribute("personId");
+        chatMessageStatusService.markMessagesAsRead(chatRoomId, personId);
+        chatRoomService.addUserToChatRoom(chatRoomId, personId);
+        return ResponseEntity.ok().build();
+    }
 }
diff --git a/src/main/java/com/chat/liveon/chat/dto/NotificationMessage.java b/src/main/java/com/chat/liveon/chat/dto/NotificationMessage.java
index 28ff5ca..6783249 100644
--- a/src/main/java/com/chat/liveon/chat/dto/NotificationMessage.java
+++ b/src/main/java/com/chat/liveon/chat/dto/NotificationMessage.java
@@ -1,4 +1,6 @@
 package com.chat.liveon.chat.dto;
 
-public class NotificationMessage {
-}
+public record NotificationMessage(
+        Long chatRoomId,
+        Long unreadCount
+) {}
diff --git a/src/main/java/com/chat/liveon/chat/dto/response/AllChatRoomResponse.java b/src/main/java/com/chat/liveon/chat/dto/response/AllChatRoomResponse.java
index f94bb92..bb2dea8 100644
--- a/src/main/java/com/chat/liveon/chat/dto/response/AllChatRoomResponse.java
+++ b/src/main/java/com/chat/liveon/chat/dto/response/AllChatRoomResponse.java
@@ -2,5 +2,6 @@
 
 public record AllChatRoomResponse(
         Long chatRoomId,
-        String chatRoomName
+        String chatRoomName,
+        Long unreadCount
 ) {}
diff --git a/src/main/java/com/chat/liveon/chat/dto/response/UnreadMessagesResponse.java b/src/main/java/com/chat/liveon/chat/dto/response/UnreadMessagesResponse.java
index 0c008ea..ab894fa 100644
--- a/src/main/java/com/chat/liveon/chat/dto/response/UnreadMessagesResponse.java
+++ b/src/main/java/com/chat/liveon/chat/dto/response/UnreadMessagesResponse.java
@@ -1,4 +1,7 @@
 package com.chat.liveon.chat.dto.response;
 
-public class UnreadMessagesResponse {
-}
+public record UnreadMessagesResponse(
+        Long chatRoomId,
+        String chatRoomName,
+        Long unreadCount
+) {}
\ No newline at end of file
diff --git a/src/main/java/com/chat/liveon/chat/entity/ChatMessageStatus.java b/src/main/java/com/chat/liveon/chat/entity/ChatMessageStatus.java
index 28408cf..d480f24 100644
--- a/src/main/java/com/chat/liveon/chat/entity/ChatMessageStatus.java
+++ b/src/main/java/com/chat/liveon/chat/entity/ChatMessageStatus.java
@@ -1,4 +1,39 @@
 package com.chat.liveon.chat.entity;
 
+import com.chat.liveon.auth.entity.Person;
+import jakarta.persistence.*;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Entity
+@Getter
+@NoArgsConstructor
 public class ChatMessageStatus {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "chat_message_id")
+    private ChatMessage chatMessage;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "person_id")
+    private Person person;
+
+    @Column(name = "is_read")
+    private boolean read;
+
+    @Builder
+    public ChatMessageStatus(ChatMessage chatMessage, Person person) {
+        this.chatMessage = chatMessage;
+        this.person = person;
+        this.read = false;
+    }
+
+    public void read() {
+        this.read = true;
+    }
 }
diff --git a/src/main/java/com/chat/liveon/chat/entity/ChatRoom.java b/src/main/java/com/chat/liveon/chat/entity/ChatRoom.java
index a974ff9..31b9f7e 100644
--- a/src/main/java/com/chat/liveon/chat/entity/ChatRoom.java
+++ b/src/main/java/com/chat/liveon/chat/entity/ChatRoom.java
@@ -6,6 +6,9 @@
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
+import java.util.HashSet;
+import java.util.Set;
+
 @Getter
 @NoArgsConstructor
 @Entity
@@ -22,9 +25,20 @@ public class ChatRoom {
     @JoinColumn(name = "person_id")
     private Person person;
 
+    @ManyToMany
+    @JoinTable(name = "chat_room_participants",
+            joinColumns = @JoinColumn(name = "chat_room_id"),
+            inverseJoinColumns = @JoinColumn(name = "person_id"))
+    private Set<Person> participants = new HashSet<>();
+
     @Builder
     public ChatRoom(String chatRoomName, Person person) {
         this.chatRoomName = chatRoomName;
         this.person = person;
     }
-}
\ No newline at end of file
+
+    public void addParticipant(Person person) {
+        participants.add(person);
+        person.getChatRooms().add(this);
+    }
+}
diff --git a/src/main/java/com/chat/liveon/chat/repository/ChatMessageStatusRepository.java b/src/main/java/com/chat/liveon/chat/repository/ChatMessageStatusRepository.java
index bd30417..b80d8c4 100644
--- a/src/main/java/com/chat/liveon/chat/repository/ChatMessageStatusRepository.java
+++ b/src/main/java/com/chat/liveon/chat/repository/ChatMessageStatusRepository.java
@@ -1,4 +1,23 @@
 package com.chat.liveon.chat.repository;
 
-public interface ChatMessageStatusRepository {
+import com.chat.liveon.chat.dto.response.UnreadMessagesResponse;
+import com.chat.liveon.chat.entity.ChatMessageStatus;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
+
+import java.util.List;
+
+public interface ChatMessageStatusRepository extends JpaRepository<ChatMessageStatus, Long> {
+    Long countByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(@Param("chatRoomId") Long chatRoomId, @Param("personId") String personId);
+
+    @Query("SELECT cms.chatMessage.chatRoom.id, cms.chatMessage.chatRoom.chatRoomName, COUNT(cms) " +
+            "FROM ChatMessageStatus cms " +
+            "WHERE cms.person.personId = :personId AND cms.read = false " +
+            "GROUP BY cms.chatMessage.chatRoom.id, cms.chatMessage.chatRoom.chatRoomName")
+    List<UnreadMessagesResponse> countUnreadMessagesByChatRoomAndPerson(@Param("personId") String personId);
+
+    List<ChatMessageStatus> findByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(Long chatRoomId, String personId);
+
 }
+
diff --git a/src/main/java/com/chat/liveon/chat/repository/ChatRoomRepository.java b/src/main/java/com/chat/liveon/chat/repository/ChatRoomRepository.java
index a45a7be..d2d40bb 100644
--- a/src/main/java/com/chat/liveon/chat/repository/ChatRoomRepository.java
+++ b/src/main/java/com/chat/liveon/chat/repository/ChatRoomRepository.java
@@ -2,11 +2,13 @@
 
 import com.chat.liveon.chat.entity.ChatRoom;
 import org.springframework.data.jpa.repository.JpaRepository;
-import org.springframework.lang.NonNull;
+import org.springframework.data.repository.query.Param;
 
+import java.util.List;
 import java.util.Optional;
 
 public interface ChatRoomRepository extends JpaRepository<ChatRoom, Long> {
-    @NonNull
     Optional<ChatRoom> findById(Long roomId);
+
+    List<ChatRoom> findByParticipants_PersonId(@Param("personId") String personId);
 }
\ No newline at end of file
diff --git a/src/main/java/com/chat/liveon/chat/service/ChatMessageService.java b/src/main/java/com/chat/liveon/chat/service/ChatMessageService.java
index 40d4217..c48ba69 100644
--- a/src/main/java/com/chat/liveon/chat/service/ChatMessageService.java
+++ b/src/main/java/com/chat/liveon/chat/service/ChatMessageService.java
@@ -2,21 +2,26 @@
 
 import com.chat.liveon.auth.entity.Person;
 import com.chat.liveon.auth.repository.PersonRepository;
+import com.chat.liveon.chat.dto.NotificationMessage;
 import com.chat.liveon.chat.dto.request.ChatMessageRequest;
 import com.chat.liveon.chat.dto.response.ChatMessageResponse;
 import com.chat.liveon.chat.entity.ChatMessage;
+import com.chat.liveon.chat.entity.ChatMessageStatus;
 import com.chat.liveon.chat.entity.ChatRoom;
 import com.chat.liveon.chat.repository.ChatMessageRepository;
+import com.chat.liveon.chat.repository.ChatMessageStatusRepository;
 import com.chat.liveon.chat.repository.ChatRoomRepository;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
+import org.springframework.messaging.simp.SimpMessagingTemplate;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @Slf4j
@@ -27,6 +32,8 @@ public class ChatMessageService {
     private final ChatMessageRepository chatMessageRepository;
     private final ChatRoomRepository chatRoomRepository;
     private final PersonRepository personRepository;
+    private final ChatMessageStatusRepository chatMessageStatusRepository;
+    private final SimpMessagingTemplate messagingTemplate;
 
     @Transactional
     public ChatMessageResponse sendMessage(Long roomId, ChatMessageRequest messageRequest) {
@@ -44,6 +51,20 @@ public ChatMessageResponse sendMessage(Long roomId, ChatMessageRequest messageRe
         chatMessage = chatMessageRepository.save(chatMessage);
         log.info("[메시지 전송 성공] 채팅방: {}, 사용자: {}, 메시지: {}", roomId, sender.getPersonName(), messageRequest.message());
 
+        Set<Person> participants = chatRoom.getParticipants();
+        for (Person person : participants) {
+            if (!person.getPersonId().equals(sender.getPersonId())) {
+                ChatMessageStatus messageStatus = ChatMessageStatus.builder()
+                        .chatMessage(chatMessage)
+                        .person(person)
+                        .build();
+                chatMessageStatusRepository.save(messageStatus);
+                long unreadCount = chatMessageStatusRepository.countByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(roomId, person.getPersonId());
+                NotificationMessage notification = new NotificationMessage(roomId, unreadCount);
+                messagingTemplate.convertAndSend("/topic/notifications/" + person.getPersonId(), notification);
+            }
+        }
+
         return new ChatMessageResponse(
                 chatMessage.getChatRoom().getId(),
                 sender.getPersonName(),
diff --git a/src/main/java/com/chat/liveon/chat/service/ChatMessageStatusService.java b/src/main/java/com/chat/liveon/chat/service/ChatMessageStatusService.java
index d089c06..8efc42f 100644
--- a/src/main/java/com/chat/liveon/chat/service/ChatMessageStatusService.java
+++ b/src/main/java/com/chat/liveon/chat/service/ChatMessageStatusService.java
@@ -1,4 +1,48 @@
 package com.chat.liveon.chat.service;
 
+import com.chat.liveon.auth.entity.Person;
+import com.chat.liveon.auth.repository.PersonRepository;
+import com.chat.liveon.chat.dto.NotificationMessage;
+import com.chat.liveon.chat.dto.response.UnreadMessagesResponse;
+import com.chat.liveon.chat.entity.ChatMessageStatus;
+import com.chat.liveon.chat.repository.ChatMessageStatusRepository;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.messaging.simp.SimpMessagingTemplate;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
 public class ChatMessageStatusService {
+
+    private final ChatMessageStatusRepository chatMessageStatusRepository;
+    private final PersonRepository personRepository;
+    private final SimpMessagingTemplate messagingTemplate;
+
+    @Transactional
+    public void markMessagesAsRead(Long chatRoomId, String personId) {
+        Person person = personRepository.findByPersonId(personId)
+                .orElseThrow(() -> new IllegalArgumentException("사용자를 찾을 수 없습니다: " + personId));
+
+        List<ChatMessageStatus> unreadMessages = chatMessageStatusRepository.findByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(chatRoomId, personId);
+        for (ChatMessageStatus messageStatus : unreadMessages) {
+            messageStatus.read();
+        }
+        chatMessageStatusRepository.saveAll(unreadMessages);
+
+        long updatedUnreadCount = chatMessageStatusRepository
+                .countByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(chatRoomId, personId);
+        NotificationMessage notification = new NotificationMessage(chatRoomId, updatedUnreadCount);
+        messagingTemplate.convertAndSend("/topic/notifications/" + person.getPersonId(), notification);
+    }
+
+    @Transactional(readOnly = true)
+    public List<UnreadMessagesResponse> getUnreadMessages(String personId) {
+        return chatMessageStatusRepository.countUnreadMessagesByChatRoomAndPerson(personId);
+    }
 }
+
diff --git a/src/main/java/com/chat/liveon/chat/service/ChatRoomService.java b/src/main/java/com/chat/liveon/chat/service/ChatRoomService.java
index fbd43c5..1e22eff 100644
--- a/src/main/java/com/chat/liveon/chat/service/ChatRoomService.java
+++ b/src/main/java/com/chat/liveon/chat/service/ChatRoomService.java
@@ -6,6 +6,7 @@
 import com.chat.liveon.chat.dto.response.AllChatRoomResponse;
 import com.chat.liveon.chat.dto.response.ChatRoomResponse;
 import com.chat.liveon.chat.entity.ChatRoom;
+import com.chat.liveon.chat.repository.ChatMessageStatusRepository;
 import com.chat.liveon.chat.repository.ChatRoomRepository;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
@@ -19,10 +20,12 @@
 public class ChatRoomService {
     private final ChatRoomRepository chatRoomRepository;
     private final PersonRepository personRepository;
+    private final ChatMessageStatusRepository chatMessageStatusRepository;
 
-    public ChatRoomService(ChatRoomRepository chatRoomRepository, PersonRepository personRepository) {
+    public ChatRoomService(ChatRoomRepository chatRoomRepository, PersonRepository personRepository, ChatMessageStatusRepository chatMessageStatusRepository) {
         this.chatRoomRepository = chatRoomRepository;
         this.personRepository = personRepository;
+        this.chatMessageStatusRepository = chatMessageStatusRepository;
     }
 
     @Transactional
@@ -34,17 +37,54 @@ public ChatRoomResponse createChatRoom(ChatRoomRequest chatRoomRequest, String p
                 .chatRoomName(chatRoomRequest.chatRoomName())
                 .person(personId)
                 .build();
-
+        chatRoom.addParticipant(personId);
+        addAllUsersToChatRoom(chatRoom);
         chatRoom = chatRoomRepository.save(chatRoom);
-        log.info("[채팅방 생성 성공] 사용자: {}, 채팅방명: {}", person, chatRoomRequest.chatRoomName());
+
         return new ChatRoomResponse(chatRoom.getId(), chatRoomRequest.chatRoomName(), personId.getId());
     }
 
     @Transactional(readOnly = true)
-    public List<AllChatRoomResponse> getAllChatRoom() {
-        List<ChatRoom> chatRooms = chatRoomRepository.findAll();
+    public List<AllChatRoomResponse> getAllChatRoom(String personId) {
+        List<ChatRoom> chatRooms = chatRoomRepository.findByParticipants_PersonId(personId);
         return chatRooms.stream()
-                .map(chatRoom -> new AllChatRoomResponse(chatRoom.getId(), chatRoom.getChatRoomName()))
+                .map(chatRoom -> {
+                    Long unreadCount = chatMessageStatusRepository.countByChatMessage_ChatRoom_IdAndPerson_PersonIdAndReadFalse(chatRoom.getId(), personId);
+                    return new AllChatRoomResponse(chatRoom.getId(), chatRoom.getChatRoomName(), unreadCount);
+                })
                 .collect(Collectors.toList());
     }
+
+    @Transactional
+    public void addUserToChatRoom(Long chatRoomId, String personId) {
+        ChatRoom chatRoom = chatRoomRepository.findById(chatRoomId)
+                .orElseThrow(() -> new RuntimeException("채팅방을 찾을 수 없습니다. ID: " + chatRoomId));
+        Person person = personRepository.findByPersonId(personId)
+                .orElseThrow(() -> new RuntimeException("사용자를 찾을 수 없습니다. personId: " + personId));
+
+        if (!chatRoom.getParticipants().contains(person)) {
+            chatRoom.addParticipant(person);
+            chatRoomRepository.save(chatRoom);
+        }
+    }
+
+    @Transactional
+    public void addUserToAllChatRooms(Person user) {
+        List<ChatRoom> allChatRooms = chatRoomRepository.findAll();
+        for (ChatRoom chatRoom : allChatRooms) {
+            if (!chatRoom.getParticipants().contains(user)) {
+                chatRoom.addParticipant(user);
+            }
+        }
+        chatRoomRepository.saveAll(allChatRooms);
+    }
+
+    private void addAllUsersToChatRoom(ChatRoom chatRoom) {
+        List<Person> allUsers = personRepository.findAll();
+        for (Person user : allUsers) {
+            if (!chatRoom.getParticipants().contains(user)) {
+                chatRoom.addParticipant(user);
+            }
+        }
+    }
 }
diff --git a/src/main/java/com/chat/liveon/config/WebConfig.java b/src/main/java/com/chat/liveon/config/WebConfig.java
index 6bc5603..6e4adfd 100644
--- a/src/main/java/com/chat/liveon/config/WebConfig.java
+++ b/src/main/java/com/chat/liveon/config/WebConfig.java
@@ -12,7 +12,7 @@ public class WebConfig implements WebMvcConfigurer {
     @Override
     public void addCorsMappings(CorsRegistry registry) {
         registry.addMapping("/**")
-                .allowedOriginPatterns("http://localhost:3000")
+                .allowedOriginPatterns("*")
                 .allowedMethods("GET", "POST", "PUT", "DELETE")
                 .allowedHeaders("*")
                 .allowCredentials(true);