diff --git a/moto/ecs/models.py b/moto/ecs/models.py
index c256d940f338..302fa2efd271 100644
--- a/moto/ecs/models.py
+++ b/moto/ecs/models.py
@@ -299,10 +299,14 @@ def create_from_cloudformation_json(  # type: ignore[misc]
             properties.get("ContainerDefinitions", []), pascal_to_camelcase
         )
         volumes = remap_nested_keys(properties.get("Volumes", []), pascal_to_camelcase)
+        memory = properties.get("Memory")
 
         ecs_backend = ecs_backends[account_id][region_name]
         return ecs_backend.register_task_definition(
-            family=family, container_definitions=container_definitions, volumes=volumes
+            family=family,
+            container_definitions=container_definitions,
+            volumes=volumes,
+            memory=memory,
         )
 
     @classmethod
@@ -320,6 +324,7 @@ def update_from_cloudformation_json(  # type: ignore[misc]
         )
         container_definitions = properties["ContainerDefinitions"]
         volumes = properties.get("Volumes")
+        memory = properties.get("Memory")
         if (
             original_resource.family != family
             or original_resource.container_definitions != container_definitions
@@ -333,6 +338,7 @@ def update_from_cloudformation_json(  # type: ignore[misc]
                 family=family,
                 container_definitions=container_definitions,
                 volumes=volumes,
+                memory=memory,
             )
         else:
             # no-op when nothing changed between old and new resources
diff --git a/tests/test_ecs/test_ecs_cloudformation.py b/tests/test_ecs/test_ecs_cloudformation.py
index 292bb3d60c1c..6617b937787a 100644
--- a/tests/test_ecs/test_ecs_cloudformation.py
+++ b/tests/test_ecs/test_ecs_cloudformation.py
@@ -2,6 +2,7 @@
 from copy import deepcopy
 
 import boto3
+import pytest
 
 from moto import mock_aws
 from moto.core.utils import pascal_to_camelcase, remap_nested_keys
@@ -366,3 +367,79 @@ def test_create_task_definition_through_cloudformation():
     assert task_definition["volumes"] == expected_properties["volumes"]
     for key, value in expected_properties["containerDefinitions"][0].items():
         assert task_definition["containerDefinitions"][0][key] == value
+
+
+@mock_aws
+def test_cloudformation_container_definition_validation():
+    cfn_conn = boto3.client("cloudformation", region_name="us-west-1")
+
+    # No task memory, no container memory
+    invalid_definition = {
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Description": "ECS Cluster Test CloudFormation",
+        "Resources": {
+            "testTaskDefinition": {
+                "Type": "AWS::ECS::TaskDefinition",
+                "Properties": {
+                    "ContainerDefinitions": [
+                        {
+                            "Name": "ecs-sample",
+                            "Image": "amazon/amazon-ecs-sample",
+                        }
+                    ],
+                },
+            }
+        },
+    }
+    invalid_json = json.dumps(invalid_definition)
+    with pytest.raises(Exception):
+        cfn_conn.create_stack(StackName="invalid-stack", TemplateBody=invalid_json)
+
+    # No task memory, has container memory
+    valid_definition = {
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Description": "ECS Cluster Test CloudFormation",
+        "Resources": {
+            "testTaskDefinition": {
+                "Type": "AWS::ECS::TaskDefinition",
+                "Properties": {
+                    "ContainerDefinitions": [
+                        {
+                            "Name": "ecs-sample",
+                            "Image": "amazon/amazon-ecs-sample",
+                            "Memory": 1024,
+                        }
+                    ],
+                },
+            }
+        },
+    }
+    valid_json = json.dumps(valid_definition)
+    name = "valid-stack-container-memory"
+    cfn_conn.create_stack(StackName=name, TemplateBody=valid_json)
+    cfn_conn.update_stack(StackName=name, TemplateBody=valid_json)
+
+    # Has task memory, no container memory
+    valid_definition = {
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Description": "ECS Cluster Test CloudFormation",
+        "Resources": {
+            "testTaskDefinition": {
+                "Type": "AWS::ECS::TaskDefinition",
+                "Properties": {
+                    "Memory": 1024,
+                    "ContainerDefinitions": [
+                        {
+                            "Name": "ecs-sample",
+                            "Image": "amazon/amazon-ecs-sample",
+                        }
+                    ],
+                },
+            }
+        },
+    }
+
+    valid_json = json.dumps(valid_definition)
+    name = "valid-stack-task-memory"
+    cfn_conn.create_stack(StackName=name, TemplateBody=valid_json)
+    cfn_conn.update_stack(StackName=name, TemplateBody=valid_json)