diff --git a/src/app/db/models/user_role.py b/src/app/db/models/user_role.py
index 44855bae..63f4b2e0 100644
--- a/src/app/db/models/user_role.py
+++ b/src/app/db/models/user_role.py
@@ -5,7 +5,7 @@
 from uuid import UUID  # noqa: TCH003
 
 from advanced_alchemy.base import UUIDAuditBase
-from sqlalchemy import ForeignKey
+from sqlalchemy import ForeignKey, UniqueConstraint
 from sqlalchemy.ext.associationproxy import AssociationProxy, association_proxy
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -18,7 +18,10 @@ class UserRole(UUIDAuditBase):
     """User Role."""
 
     __tablename__ = "user_account_role"
-    __table_args__ = {"comment": "Links a user to a specific role."}
+    __table_args__ = (
+        UniqueConstraint("user_id", "role_id"),  # Avoid multiple assignments of the same role
+        {"comment": "Links a user to a specific role."},
+    )
     user_id: Mapped[UUID] = mapped_column(ForeignKey("user_account.id", ondelete="cascade"), nullable=False)
     role_id: Mapped[UUID] = mapped_column(ForeignKey("role.id", ondelete="cascade"), nullable=False)
     assigned_at: Mapped[datetime] = mapped_column(default=datetime.now(UTC))
diff --git a/src/app/domain/accounts/controllers/user_role.py b/src/app/domain/accounts/controllers/user_role.py
index fb794318..5e131667 100644
--- a/src/app/domain/accounts/controllers/user_role.py
+++ b/src/app/domain/accounts/controllers/user_role.py
@@ -1,4 +1,5 @@
 """User Routes."""
+
 from __future__ import annotations
 
 from litestar import Controller, post
@@ -44,8 +45,11 @@ async def assign_role(
         """Create a new migration role."""
         role_id = (await roles_service.get_one(slug=role_slug)).id
         user_obj = await users_service.get_one(email=data.user_name)
-        if all(user_role.role_id != role_id for user_role in user_obj.roles):
-            obj, created = await user_roles_service.get_or_upsert(role_id=role_id, user_id=user_obj.id)
+        # if all(user_role.role_id != role_id for user_role in user_obj.roles):
+        obj, created = await user_roles_service.get_or_upsert(
+            role_id=role_id,
+            user_id=user_obj.id,
+        )
         if created:
             return Message(message=f"Successfully assigned the '{obj.role_slug}' role to {obj.user_email}.")
         return Message(message=f"User {obj.user_email} already has the '{obj.role_slug}' role.")
diff --git a/tests/integration/test_account_role.py b/tests/integration/test_account_role.py
index 1b1fcf54..e0f5efa3 100644
--- a/tests/integration/test_account_role.py
+++ b/tests/integration/test_account_role.py
@@ -1,11 +1,12 @@
 from __future__ import annotations
 
+import asyncio
 from typing import TYPE_CHECKING
 
 import pytest
 
 if TYPE_CHECKING:
-    from httpx import AsyncClient
+    from httpx import AsyncClient, Response
 
 
 pytestmark = pytest.mark.anyio
@@ -66,3 +67,28 @@ async def test_superuser_role_access(
     response = await client.get("/api/teams", headers=user_token_headers)
     assert response.status_code == 200
     assert int(response.json()["total"]) == 0
+
+
+@pytest.mark.parametrize("n_requests", [1, 4])
+async def test_assign_role_concurrent(
+    client: "AsyncClient",
+    superuser_token_headers: dict[str, str],
+    n_requests: int,
+) -> None:
+    async def post() -> Response:
+        return await client.post(
+            "/api/roles/superuser/assign",
+            json={"userName": "user@example.com"},
+            headers=superuser_token_headers,
+        )
+
+    responses = await asyncio.gather(*[post() for _ in range(n_requests)])
+
+    assert all(res.status_code == 201 for res in responses)
+    messages = [res.json()["message"] for res in responses]
+    assert "Successfully assigned the 'superuser' role to user@example.com." in messages
+
+    responses = await asyncio.gather(*[post() for _ in range(n_requests)])
+    assert all(res.status_code == 201 for res in responses)
+    messages = [res.json()["message"] for res in responses]
+    assert all(msg == "User user@example.com already has the 'superuser' role." for msg in messages)