diff --git a/API_SQLuedo/API/Controllers/UserController.cs b/API_SQLuedo/API/Controllers/UserController.cs
index 0d8a3cc..c2442a7 100644
--- a/API_SQLuedo/API/Controllers/UserController.cs
+++ b/API_SQLuedo/API/Controllers/UserController.cs
@@ -157,6 +157,16 @@ namespace API.Controllers
                 return BadRequest();
             }
 
+            if (userService.IsEmailTaken(dto.Email))
+            {
+                return BadRequest("Email déjà utilisé");
+            }
+
+            if (userService.IsUsernameTaken(dto.Username))
+            {
+                return BadRequest("Username déjà utilisé");
+            }
+
             // return Ok(userService.CreateUser(username, password, email, isAdmin));
             logger.LogInformation(
                 "[INFORMATION] Un utilisateur a été créé : username - {username}, password - {password}, email - {email}, isAdmin - {isAdmin}",
diff --git a/API_SQLuedo/API/Service/UserDataServiceAPI.cs b/API_SQLuedo/API/Service/UserDataServiceAPI.cs
index 273e5f0..1102048 100644
--- a/API_SQLuedo/API/Service/UserDataServiceAPI.cs
+++ b/API_SQLuedo/API/Service/UserDataServiceAPI.cs
@@ -38,4 +38,8 @@ public class UserDataServiceApi(IUserService<UserEntity> userService) : IUserSer
 
     public UserDto CreateUser(string username, string password, string email, bool isAdmin) =>
         userService.CreateUser(username, password, email, isAdmin).FromEntityToDto();
+
+    public bool IsEmailTaken(string email) => userService.IsEmailTaken(email);
+
+    public bool IsUsernameTaken(string username) => userService.IsUsernameTaken(username);
 }
\ No newline at end of file
diff --git a/API_SQLuedo/DbDataManager/Service/UserDataService.cs b/API_SQLuedo/DbDataManager/Service/UserDataService.cs
index 4676d15..ac3b606 100644
--- a/API_SQLuedo/DbDataManager/Service/UserDataService.cs
+++ b/API_SQLuedo/DbDataManager/Service/UserDataService.cs
@@ -179,4 +179,16 @@ public class UserDataService : IUserService<UserEntity>
         DbContext.SaveChangesAsync();
         return newUserEntity;
     }
+
+    public bool IsEmailTaken(string email)
+    {
+        var isEmail = DbContext.Users.Any(u => u.Email == email);
+        return isEmail;
+    }
+
+    public bool IsUsernameTaken(string username)
+    {
+        var isUsername = DbContext.Users.Any(u => u.Username == username);
+        return isUsername;
+    }
 }
\ No newline at end of file
diff --git a/API_SQLuedo/Shared/IUserService.cs b/API_SQLuedo/Shared/IUserService.cs
index 06051a9..4c4b10c 100644
--- a/API_SQLuedo/Shared/IUserService.cs
+++ b/API_SQLuedo/Shared/IUserService.cs
@@ -14,5 +14,7 @@ namespace Shared
         public bool DeleteUserByUsername(string username);
         public TUser UpdateUser(int id, TUser user);
         public TUser CreateUser(string username, string password, string email, bool isAdmin);
+        public bool IsEmailTaken(string email);
+        public bool IsUsernameTaken(string username);
     }
 }
\ No newline at end of file