diff --git a/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs b/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
index dcc3c65..47c04e7 100644
--- a/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
+++ b/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
@@ -355,6 +355,122 @@ public class ActivityPubDeliveryService(
         return successCount > 0;
     }
 
+    public async Task<bool> SendLikeActivityToLocalPostAsync(
+        Guid publisherId,
+        Guid postId,
+        Guid actorId
+    )
+    {
+        var publisher = await db.Publishers
+            .Include(p => p.Members)
+            .FirstOrDefaultAsync(p => p.Id == publisherId);
+
+        if (publisher == null)
+            return false;
+
+        var publisherActor = await GetLocalActorAsync(publisherId);
+        if (publisherActor == null)
+            return false;
+
+        var actor = await db.FediverseActors
+            .FirstOrDefaultAsync(a => a.Id == actorId);
+
+        if (actor == null)
+            return false;
+
+        var actorUrl = publisherActor.Uri;
+        var postUrl = $"https://{Domain}/posts/{postId}";
+
+        var activity = new Dictionary<string, object>
+        {
+            ["@context"] = "https://www.w3.org/ns/activitystreams",
+            ["id"] = $"{actorUrl}/likes/{Guid.NewGuid()}",
+            ["type"] = "Like",
+            ["actor"] = actor.Uri,
+            ["object"] = postUrl,
+            ["to"] = new[] { "https://www.w3.org/ns/activitystreams#Public" },
+            ["cc"] = new[] { $"{actorUrl}/followers" }
+        };
+
+        var followers = await db.FediverseRelationships
+            .Include(r => r.TargetActor)
+            .Where(r => r.ActorId == publisherActor.Id && r.IsFollowedBy)
+            .Select(r => r.TargetActor)
+            .ToListAsync();
+
+        var successCount = 0;
+
+        foreach (var follower in followers)
+        {
+            if (follower.InboxUri == null) continue;
+            var success = await SendActivityToInboxAsync(activity, follower.InboxUri, actorUrl);
+            if (success)
+                successCount++;
+        }
+
+        logger.LogInformation("Sent Like activity for post {PostId} to {Count}/{Total} followers",
+            postId, successCount, followers.Count);
+
+        return successCount > 0;
+    }
+
+    public async Task<bool> SendUndoLikeActivityAsync(
+        Guid publisherId,
+        Guid postId,
+        string likeActivityId
+    )
+    {
+        var publisher = await db.Publishers
+            .Include(p => p.Members)
+            .FirstOrDefaultAsync(p => p.Id == publisherId);
+
+        if (publisher == null)
+            return false;
+
+        var publisherActor = await GetLocalActorAsync(publisherId);
+        if (publisherActor == null)
+            return false;
+
+        var actorUrl = publisherActor.Uri;
+        var postUrl = $"https://{Domain}/posts/{postId}";
+
+        var activity = new Dictionary<string, object>
+        {
+            ["@context"] = "https://www.w3.org/ns/activitystreams",
+            ["id"] = $"{actorUrl}/undo/{Guid.NewGuid()}",
+            ["type"] = "Undo",
+            ["actor"] = actorUrl,
+            ["object"] = new Dictionary<string, object>
+            {
+                ["type"] = "Like",
+                ["object"] = postUrl
+            },
+            ["to"] = new[] { "https://www.w3.org/ns/activitystreams#Public" },
+            ["cc"] = new[] { $"{actorUrl}/followers" }
+        };
+
+        var followers = await db.FediverseRelationships
+            .Include(r => r.TargetActor)
+            .Where(r => r.ActorId == publisherActor.Id && r.IsFollowedBy)
+            .Select(r => r.TargetActor)
+            .ToListAsync();
+
+        var successCount = 0;
+
+        foreach (var follower in followers)
+        {
+            if (follower.InboxUri == null) continue;
+            var success = await SendActivityToInboxAsync(activity, follower.InboxUri, actorUrl);
+            if (success)
+                successCount++;
+        }
+
+        logger.LogInformation("Sent Undo Like activity for post {PostId} to {Count}/{Total} followers",
+            postId, successCount, followers.Count);
+
+        return successCount > 0;
+    }
+
     public async Task<bool> SendLikeActivityAsync(
         Guid postId,
         Guid accountId,
diff --git a/DysonNetwork.Sphere/Post/PostService.cs b/DysonNetwork.Sphere/Post/PostService.cs
index 829a0ec..ffef682 100644
--- a/DysonNetwork.Sphere/Post/PostService.cs
+++ b/DysonNetwork.Sphere/Post/PostService.cs
@@ -26,7 +26,8 @@ public partial class PostService(
     FileReferenceService.FileReferenceServiceClient fileRefs,
     Publisher.PublisherService ps,
     WebReaderService reader,
-    AccountService.AccountServiceClient accounts
+    AccountService.AccountServiceClient accounts,
+    ActivityPub.ActivityPubDeliveryService activityPubDeliveryService
 )
 {
     private const string PostFileUsageIdentifier = "post";
@@ -582,6 +583,66 @@ public partial class PostService(
 
         await db.SaveChangesAsync();
 
+        // Send ActivityPub Like/Undo activities if post's publisher has actor
+        if (post.PublisherId.HasValue && reaction.AccountId.HasValue)
+        {
+            var publisherActor = await activityPubDeliveryService.GetLocalActorAsync(post.PublisherId.Value);
+
+            if (publisherActor != null && reaction.Attitude == Shared.Models.PostReactionAttitude.Positive)
+            {
+                var likerActor = await db.FediverseActors
+                    .FirstOrDefaultAsync(a => a.PublisherId.HasValue && a.PublisherId.Value == reaction.AccountId.Value);
+
+                if (likerActor != null)
+                {
+                    if (!isRemoving)
+                    {
+                        // Sending Like - deliver to publisher's remote followers
+                        _ = Task.Run(async () =>
+                        {
+                            try
+                            {
+                                using var scope = factory.CreateScope();
+                                var deliveryService = scope.ServiceProvider
+                                    .GetRequiredService<ActivityPubDeliveryService>();
+                                await deliveryService.SendLikeActivityToLocalPostAsync(
+                                    post.PublisherId.Value,
+                                    post.Id,
+                                    likerActor.Id
+                                );
+                            }
+                            catch (Exception ex)
+                            {
+                                logger.LogError($"Error sending ActivityPub Like: {ex.Message}");
+                            }
+                        });
+                    }
+                    else
+                    {
+                        // Sending Undo Like - deliver to publisher's remote followers
+                        _ = Task.Run(async () =>
+                        {
+                            try
+                            {
+                                using var scope = factory.CreateScope();
+                                var deliveryService = scope.ServiceProvider
+                                    .GetRequiredService<ActivityPubDeliveryService>();
+                                await deliveryService.SendUndoLikeActivityAsync(
+                                    post.PublisherId.Value,
+                                    post.Id,
+                                    string.Empty
+                                );
+                            }
+                            catch (Exception ex)
+                            {
+                                logger.LogError($"Error sending ActivityPub Undo Like: {ex.Message}");
+                            }
+                        });
+                    }
+                }
+            }
+        }
+
         if (!isSelfReact)
             _ = Task.Run(async () =>
             {