diff --git a/app/models/__init__.py b/app/models/__init__.py
index e69de29..d478f39 100644
--- a/app/models/__init__.py
+++ b/app/models/__init__.py
@@ -0,0 +1,2 @@
+from .todo import Todo
+from .user import User
diff --git a/app/repositories/users.py b/app/repositories/users.py
index 0fa5998..8e38d04 100644
--- a/app/repositories/users.py
+++ b/app/repositories/users.py
@@ -1,8 +1,10 @@
 from typing import List
 
-from app.models.user import User
+from app.models import Todo, User
 
-user_list: List[User] = [User("id", "Jane Doe"), User(username="John Doe")]
+jane = User("id", "Jane Doe")
+jane.tasks = [Todo(title="Test")]
+user_list: List[User] = [jane, User(username="John Doe")]
 
 
 def get_all_users() -> List[User]:
@@ -36,3 +38,8 @@ def remove_user(user_id: str) -> User:
     user = get_user_by_id(user_id)
     index = user_list.index(user)
     return user_list.pop(index)
+
+
+def add_todo_to_user(todo: Todo, user: User) -> bool:
+    user.tasks.append(todo)
+    return True
diff --git a/app/schema/mutations/mutation.py b/app/schema/mutations/mutation.py
index a11941e..2092135 100644
--- a/app/schema/mutations/mutation.py
+++ b/app/schema/mutations/mutation.py
@@ -1,7 +1,12 @@
 import graphene
 
 from app.schema.mutations.todo import CreateTodo, DeleteTodo, CloseTodo, UpdateTodo
-from app.schema.mutations.user import CreateUser, UpdateUser, DeleteUser
+from app.schema.mutations.user import (
+    CreateUser,
+    UpdateUser,
+    DeleteUser,
+    AssignTodoToUser,
+)
 
 
 class Mutation(graphene.ObjectType):
@@ -14,3 +19,4 @@ class Mutation(graphene.ObjectType):
     create_user = CreateUser.Field()
     update_user = UpdateUser.Field()
     delete_user = DeleteUser.Field()
+    assign_todo_to_user = AssignTodoToUser.Field()
diff --git a/app/schema/mutations/todo/close_todo.py b/app/schema/mutations/todo/close_todo.py
index 5b9586a..2eb4a25 100644
--- a/app/schema/mutations/todo/close_todo.py
+++ b/app/schema/mutations/todo/close_todo.py
@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.todo import TodoResponseField
-from app.usecases.todo.close_todo import close_todo
+from app.usecases.todo import close_todo
 
 
 class CloseTodo(graphene.Mutation):
diff --git a/app/schema/mutations/todo/create_todo.py b/app/schema/mutations/todo/create_todo.py
index dc416fc..a0875c8 100644
--- a/app/schema/mutations/todo/create_todo.py
+++ b/app/schema/mutations/todo/create_todo.py
@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.todo import TodoResponseField
-from app.usecases import create_todo
+from app.usecases.todo import create_todo
 
 
 class CreateTodo(graphene.Mutation):
diff --git a/app/schema/mutations/todo/delete_todo.py b/app/schema/mutations/todo/delete_todo.py
index fabe525..6daeeee 100644
--- a/app/schema/mutations/todo/delete_todo.py
+++ b/app/schema/mutations/todo/delete_todo.py
@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.todo import TodoResponseField
-from app.usecases import delete_todo
+from app.usecases.todo import delete_todo
 
 
 class DeleteTodo(graphene.Mutation):
diff --git a/app/schema/mutations/todo/update_todo.py b/app/schema/mutations/todo/update_todo.py
index dbe2664..dc47494 100644
--- a/app/schema/mutations/todo/update_todo.py
+++ b/app/schema/mutations/todo/update_todo.py
@@ -2,7 +2,7 @@ import graphene
 
 from app.models.todo import Todo
 from app.schema.types.todo import TodoInputType, TodoResponseField
-from app.usecases import update_todo
+from app.usecases.todo import update_todo
 
 
 class UpdateTodo(graphene.Mutation):
diff --git a/app/schema/mutations/user/__init__.py b/app/schema/mutations/user/__init__.py
index 98b8b56..1f63ca8 100644
--- a/app/schema/mutations/user/__init__.py
+++ b/app/schema/mutations/user/__init__.py
@@ -1,3 +1,4 @@
 from .create_user import CreateUser
 from .delete_user import DeleteUser
 from .update_user import UpdateUser
+from .assign_todo_to_user import AssignTodoToUser
diff --git a/app/schema/mutations/user/assign_todo_to_user.py b/app/schema/mutations/user/assign_todo_to_user.py
new file mode 100644
index 0000000..2c2e51d
--- /dev/null
+++ b/app/schema/mutations/user/assign_todo_to_user.py
@@ -0,0 +1,20 @@
+import graphene
+
+from app.schema.types.response import ResponseField
+from app.usecases.user import assign_todo_to_user
+
+
+class AssignTodoToUser(graphene.Mutation):
+    class Arguments:
+        todo_id = graphene.String()
+        user_id = graphene.String()
+
+    result = graphene.Field(ResponseField)
+
+    def mutate(self, info, todo_id: str, user_id: str):
+        is_success = assign_todo_to_user(user_id=user_id, todo_id=todo_id)
+        error_message = "Cannot assign todo to user." if not is_success else None
+
+        return AssignTodoToUser(
+            ResponseField(is_success=is_success, error_message=error_message)
+        )
diff --git a/app/schema/mutations/user/create_user.py b/app/schema/mutations/user/create_user.py
index 0697c84..0b27f90 100644
--- a/app/schema/mutations/user/create_user.py
+++ b/app/schema/mutations/user/create_user.py
@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.user import UserResponseField
-from app.usecases.user.create_user import create_user
+from app.usecases.user import create_user
 
 
 class CreateUser(graphene.Mutation):
diff --git a/app/schema/mutations/user/delete_user.py b/app/schema/mutations/user/delete_user.py
index b645427..19660ce 100644
--- a/app/schema/mutations/user/delete_user.py
+++ b/app/schema/mutations/user/delete_user.py
@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.user import UserResponseField
-from app.usecases.user.delete_user import delete_user
+from app.usecases.user import delete_user
 
 
 class DeleteUser(graphene.Mutation):
diff --git a/app/schema/mutations/user/update_user.py b/app/schema/mutations/user/update_user.py
index 837ed37..876713c 100644
--- a/app/schema/mutations/user/update_user.py
+++ b/app/schema/mutations/user/update_user.py
@@ -2,7 +2,7 @@ import graphene
 
 from app.models.user import User
 from app.schema.types.user import UserInputType, UserResponseField
-from app.usecases.user.update_user import update_user
+from app.usecases.user import update_user
 
 
 class UpdateUser(graphene.Mutation):
diff --git a/app/schema/queries/todo.py b/app/schema/queries/todo.py
index 2608c94..d2d9efa 100644
--- a/app/schema/queries/todo.py
+++ b/app/schema/queries/todo.py
@@ -3,7 +3,7 @@ Defines the query and how to interact with
 """
 
 from app.schema.types.todo import TodoResponseField, TodoListResponseField
-from app.usecases import read_all_todos, read_todo_by_id
+from app.usecases.todo import read_all_todos, read_todo_by_id
 
 
 def resolve_list_todos(self, info) -> TodoListResponseField:
diff --git a/app/schema/queries/user.py b/app/schema/queries/user.py
index 82486a8..5c773f6 100644
--- a/app/schema/queries/user.py
+++ b/app/schema/queries/user.py
@@ -1,6 +1,5 @@
 from app.schema.types.user import UserListResponseField, UserResponseField
-from app.usecases.user.read_all_users import read_all_users
-from app.usecases.user.read_user_by_id import read_user_by_id
+from app.usecases.user import read_all_users, read_user_by_id
 
 
 def resolve_list_users(self, info):
@@ -9,5 +8,5 @@ def resolve_list_users(self, info):
 
 
 def resolve_get_user(self, info, user_id: str):
-    user = read_user_by_id(user_id)
+    user, _ = read_user_by_id(user_id)
     return UserResponseField(user=user)
diff --git a/app/schema/types/user.py b/app/schema/types/user.py
index 736dd17..fded72b 100644
--- a/app/schema/types/user.py
+++ b/app/schema/types/user.py
@@ -1,11 +1,13 @@
 import graphene
 
 from app.schema.types.response import ResponseField
+from app.schema.types.todo import TodoType
 
 
 class UserType(graphene.ObjectType):
     user_id = graphene.String()
     username = graphene.String()
+    tasks = graphene.List(TodoType)
 
 
 class UserInputType(graphene.InputObjectType):
diff --git a/app/usecases/__init__.py b/app/usecases/__init__.py
index eca73bb..e69de29 100644
--- a/app/usecases/__init__.py
+++ b/app/usecases/__init__.py
@@ -1,6 +0,0 @@
-from app.usecases.todo.close_todo import close_todo
-from app.usecases.todo.create_todo import create_todo
-from app.usecases.todo.delete_todo import delete_todo
-from app.usecases.todo.read_all_todos import read_all_todos
-from app.usecases.todo.read_todo_by_id import read_todo_by_id
-from app.usecases.todo.update_todo import update_todo
diff --git a/app/usecases/todo/__init__.py b/app/usecases/todo/__init__.py
index e69de29..eca73bb 100644
--- a/app/usecases/todo/__init__.py
+++ b/app/usecases/todo/__init__.py
@@ -0,0 +1,6 @@
+from app.usecases.todo.close_todo import close_todo
+from app.usecases.todo.create_todo import create_todo
+from app.usecases.todo.delete_todo import delete_todo
+from app.usecases.todo.read_all_todos import read_all_todos
+from app.usecases.todo.read_todo_by_id import read_todo_by_id
+from app.usecases.todo.update_todo import update_todo
diff --git a/app/usecases/user/__init__.py b/app/usecases/user/__init__.py
index e69de29..8ef089f 100644
--- a/app/usecases/user/__init__.py
+++ b/app/usecases/user/__init__.py
@@ -0,0 +1,6 @@
+from .assign_todo_to_user import assign_todo_to_user
+from .create_user import create_user
+from .delete_user import delete_user
+from .read_all_users import read_all_users
+from .read_user_by_id import read_user_by_id
+from .update_user import update_user
diff --git a/app/usecases/user/assign_todo_to_user.py b/app/usecases/user/assign_todo_to_user.py
new file mode 100644
index 0000000..09b8c40
--- /dev/null
+++ b/app/usecases/user/assign_todo_to_user.py
@@ -0,0 +1,15 @@
+from app.repositories.users import add_todo_to_user
+from app.usecases.todo import read_todo_by_id
+from app.usecases.user.read_user_by_id import read_user_by_id
+
+
+def assign_todo_to_user(user_id: str, todo_id: str) -> bool:
+    user, is_success = read_user_by_id(user_id)
+    if not is_success:
+        return False
+
+    todo, is_success = read_todo_by_id(todo_id)
+    if not is_success:
+        return False
+
+    return add_todo_to_user(todo, user)
diff --git a/app/usecases/user/read_user_by_id.py b/app/usecases/user/read_user_by_id.py
index 939a658..afef6e7 100644
--- a/app/usecases/user/read_user_by_id.py
+++ b/app/usecases/user/read_user_by_id.py
@@ -1,6 +1,11 @@
+from typing import Tuple
+
 from app.models.user import User
 from app.repositories.users import get_user_by_id
 
 
-def read_user_by_id(user_id: str) -> User:
-    return get_user_by_id(user_id)
+def read_user_by_id(user_id: str) -> Tuple[User, bool]:
+    try:
+        return get_user_by_id(user_id), True
+    except IndexError:
+        return None, False