diff --git a/MareSynchronos/Services/DalamudUtilService.cs b/MareSynchronos/Services/DalamudUtilService.cs
index 8a14334..2c3a4cd 100644
--- a/MareSynchronos/Services/DalamudUtilService.cs
+++ b/MareSynchronos/Services/DalamudUtilService.cs
@@ -22,6 +22,7 @@ public class DalamudUtilService : IHostedService, IMediatorSubscriber
     private readonly List<uint> _classJobIdsIgnoredForPets = [30];
     private readonly IClientState _clientState;
     private readonly ICondition _condition;
+    private readonly IDataManager _gameData;
     private readonly IFramework _framework;
     private readonly IGameGui _gameGui;
     private readonly ILogger<DalamudUtilService> _logger;
@@ -46,6 +47,7 @@ public class DalamudUtilService : IHostedService, IMediatorSubscriber
         _framework = framework;
         _gameGui = gameGui;
         _condition = condition;
+        _gameData = gameData;
         Mediator = mediator;
         _performanceCollector = performanceCollector;
         WorldData = new(() =>
@@ -77,6 +79,7 @@ public class DalamudUtilService : IHostedService, IMediatorSubscriber
     public bool IsOnFrameworkThread => _framework.IsInFrameworkUpdateThread;
     public bool IsZoning => _condition[ConditionFlag.BetweenAreas] || _condition[ConditionFlag.BetweenAreas51];
     public bool IsInCombatOrPerforming { get; private set; } = false;
+    public bool HasModifiedGameFiles => _gameData.HasModifiedGameDataFiles;
 
     public Lazy<Dictionary<ushort, string>> WorldData { get; private set; }
 
diff --git a/MareSynchronos/WebAPI/SignalR/ApiController.cs b/MareSynchronos/WebAPI/SignalR/ApiController.cs
index dbe3a2a..ce7ba12 100644
--- a/MareSynchronos/WebAPI/SignalR/ApiController.cs
+++ b/MareSynchronos/WebAPI/SignalR/ApiController.cs
@@ -204,6 +204,14 @@ public sealed partial class ApiController : DisposableMediatorSubscriberBase, IM
                         Dalamud.Interface.Internal.Notifications.NotificationType.Warning));
                 }
 
+                if (_dalamudUtil.HasModifiedGameFiles)
+                {
+                    Mediator.Publish(new NotificationMessage("Modified Game Files detected",
+                        "Mare has detected modified game files in your FFXIV installation. You will be able to connect, but the synchronization functionality might be (partially) broken. " +
+                        "Exit the game and repair it through XIVLauncher to get rid of this message.",
+                        Dalamud.Interface.Internal.Notifications.NotificationType.Error));
+                }
+
                 await LoadIninitialPairs().ConfigureAwait(false);
                 await LoadOnlinePairs().ConfigureAwait(false);
             }