diff --git a/java/com/google/gerrit/acceptance/ExtensionRegistry.java b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
index 0acf3bc..3d90bf0 100644
--- a/java/com/google/gerrit/acceptance/ExtensionRegistry.java
+++ b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
@@ -21,6 +21,7 @@
 import com.google.gerrit.extensions.config.PluginProjectPermissionDefinition;
 import com.google.gerrit.extensions.events.AccountActivationListener;
 import com.google.gerrit.extensions.events.AccountIndexedListener;
+import com.google.gerrit.extensions.events.AttentionSetListener;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
 import com.google.gerrit.extensions.events.CommentAddedListener;
 import com.google.gerrit.extensions.events.GitBatchRefUpdateListener;
@@ -103,6 +104,7 @@
   private final DynamicSet<OnPostReview> onPostReviews;
   private final DynamicSet<ReviewerAddedListener> reviewerAddedListeners;
   private final DynamicSet<ReviewerDeletedListener> reviewerDeletedListeners;
+  private final DynamicSet<AttentionSetListener> attentionSetListeners;
 
   private final DynamicMap<ChangeHasOperandFactory> hasOperands;
   private final DynamicMap<ChangeIsOperandFactory> isOperands;
@@ -147,7 +149,8 @@
       DynamicSet<ReviewerAddedListener> reviewerAddedListeners,
       DynamicSet<ReviewerDeletedListener> reviewerDeletedListeners,
       DynamicMap<ChangeHasOperandFactory> hasOperands,
-      DynamicMap<ChangeIsOperandFactory> isOperands) {
+      DynamicMap<ChangeIsOperandFactory> isOperands,
+      DynamicSet<AttentionSetListener> attentionSetListeners) {
     this.accountIndexedListeners = accountIndexedListeners;
     this.changeIndexedListeners = changeIndexedListeners;
     this.groupIndexedListeners = groupIndexedListeners;
@@ -187,6 +190,7 @@
     this.reviewerDeletedListeners = reviewerDeletedListeners;
     this.hasOperands = hasOperands;
     this.isOperands = isOperands;
+    this.attentionSetListeners = attentionSetListeners;
   }
 
   public Registration newRegistration() {
@@ -330,6 +334,10 @@
       return add(workInProgressStateChangedListeners, workInProgressStateChangedListener);
     }
 
+    public Registration add(AttentionSetListener attentionSetListener) {
+      return add(attentionSetListeners, attentionSetListener);
+    }
+
     public Registration add(CapabilityDefinition capabilityDefinition, String exportName) {
       return add(capabilityDefinitions, capabilityDefinition, exportName);
     }
diff --git a/java/com/google/gerrit/extensions/events/AttentionSetListener.java b/java/com/google/gerrit/extensions/events/AttentionSetListener.java
new file mode 100644
index 0000000..ada30ce
--- /dev/null
+++ b/java/com/google/gerrit/extensions/events/AttentionSetListener.java
@@ -0,0 +1,46 @@
+// Copyright (C) 2022 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.events;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+import java.util.Set;
+
+/** Notified whenever the attention set is changed. */
+@ExtensionPoint
+public interface AttentionSetListener {
+  interface Event extends ChangeEvent {
+
+    /**
+     * Returns the users added to the attention set because of this change
+     *
+     * @return Account IDs
+     */
+    Set<Integer> usersAdded();
+
+    /**
+     * Returns the users removed from the attention set because of this change
+     *
+     * @return Account IDs
+     */
+    Set<Integer> usersRemoved();
+  }
+
+  /**
+   * This function will be called when the attention set changes
+   *
+   * @param event The event that changed the attention set
+   */
+  void onAttentionSetChanged(Event event);
+}
diff --git a/java/com/google/gerrit/server/change/AddToAttentionSetOp.java b/java/com/google/gerrit/server/change/AddToAttentionSetOp.java
index 1cf31c1..1acc91d 100644
--- a/java/com/google/gerrit/server/change/AddToAttentionSetOp.java
+++ b/java/com/google/gerrit/server/change/AddToAttentionSetOp.java
@@ -20,6 +20,7 @@
 import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.extensions.events.AttentionSetObserver;
 import com.google.gerrit.server.mail.send.AddToAttentionSetSender;
 import com.google.gerrit.server.notedb.ChangeUpdate;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -39,6 +40,7 @@
   private final ChangeData.Factory changeDataFactory;
   private final AddToAttentionSetSender.Factory addToAttentionSetSender;
   private final AttentionSetEmail.Factory attentionSetEmailFactory;
+  private final AttentionSetObserver attentionSetObserver;
 
   private final Account.Id attentionUserId;
   private final String reason;
@@ -58,12 +60,14 @@
       ChangeData.Factory changeDataFactory,
       AddToAttentionSetSender.Factory addToAttentionSetSender,
       AttentionSetEmail.Factory attentionSetEmailFactory,
+      AttentionSetObserver attentionSetObserver,
       @Assisted Account.Id attentionUserId,
       @Assisted String reason,
       @Assisted boolean notify) {
     this.changeDataFactory = changeDataFactory;
     this.addToAttentionSetSender = addToAttentionSetSender;
     this.attentionSetEmailFactory = attentionSetEmailFactory;
+    this.attentionSetObserver = attentionSetObserver;
 
     this.attentionUserId = requireNonNull(attentionUserId, "user");
     this.reason = requireNonNull(reason, "reason");
@@ -85,10 +89,13 @@
 
     change = ctx.getChange();
 
-    ChangeUpdate update = ctx.getUpdate(ctx.getChange().currentPatchSetId());
-    update.addToPlannedAttentionSetUpdates(
+    ChangeUpdate changeUpdate = ctx.getUpdate(ctx.getChange().currentPatchSetId());
+    AttentionSetUpdate attentionUpdate =
         AttentionSetUpdate.createForWrite(
-            attentionUserId, AttentionSetUpdate.Operation.ADD, reason));
+            attentionUserId, AttentionSetUpdate.Operation.ADD, reason);
+    changeUpdate.addToPlannedAttentionSetUpdates(attentionUpdate);
+    attentionSetObserver.fire(
+        changeDataFactory.create(change), ctx.getAccount(), attentionUpdate, ctx.getWhen());
     return true;
   }
 
diff --git a/java/com/google/gerrit/server/change/RemoveFromAttentionSetOp.java b/java/com/google/gerrit/server/change/RemoveFromAttentionSetOp.java
index 9fb4fc4..2305791 100644
--- a/java/com/google/gerrit/server/change/RemoveFromAttentionSetOp.java
+++ b/java/com/google/gerrit/server/change/RemoveFromAttentionSetOp.java
@@ -21,6 +21,7 @@
 import com.google.gerrit.entities.AttentionSetUpdate.Operation;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.extensions.events.AttentionSetObserver;
 import com.google.gerrit.server.mail.send.RemoveFromAttentionSetSender;
 import com.google.gerrit.server.notedb.ChangeUpdate;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -41,6 +42,7 @@
   private final ChangeData.Factory changeDataFactory;
   private final RemoveFromAttentionSetSender.Factory removeFromAttentionSetSender;
   private final AttentionSetEmail.Factory attentionSetEmailFactory;
+  private final AttentionSetObserver attentionSetObserver;
 
   private final Account.Id attentionUserId;
   private final String reason;
@@ -60,12 +62,14 @@
       ChangeData.Factory changeDataFactory,
       RemoveFromAttentionSetSender.Factory removeFromAttentionSetSenderFactory,
       AttentionSetEmail.Factory attentionSetEmailFactory,
+      AttentionSetObserver attentionSetObserver,
       @Assisted Account.Id attentionUserId,
       @Assisted String reason,
       @Assisted boolean notify) {
     this.changeDataFactory = changeDataFactory;
     this.removeFromAttentionSetSender = removeFromAttentionSetSenderFactory;
     this.attentionSetEmailFactory = attentionSetEmailFactory;
+    this.attentionSetObserver = attentionSetObserver;
     this.attentionUserId = requireNonNull(attentionUserId, "user");
     this.reason = requireNonNull(reason, "reason");
     this.notify = notify;
@@ -86,9 +90,12 @@
 
     change = ctx.getChange();
 
-    ChangeUpdate update = ctx.getUpdate(ctx.getChange().currentPatchSetId());
-    update.addToPlannedAttentionSetUpdates(
-        AttentionSetUpdate.createForWrite(attentionUserId, Operation.REMOVE, reason));
+    ChangeUpdate changeUpdate = ctx.getUpdate(ctx.getChange().currentPatchSetId());
+    AttentionSetUpdate attentionUpdate =
+        AttentionSetUpdate.createForWrite(attentionUserId, Operation.REMOVE, reason);
+    changeUpdate.addToPlannedAttentionSetUpdates(attentionUpdate);
+    attentionSetObserver.fire(
+        changeDataFactory.create(change), ctx.getAccount(), attentionUpdate, ctx.getWhen());
     return true;
   }
 
diff --git a/java/com/google/gerrit/server/config/GerritGlobalModule.java b/java/com/google/gerrit/server/config/GerritGlobalModule.java
index a750d8e..fa381ad 100644
--- a/java/com/google/gerrit/server/config/GerritGlobalModule.java
+++ b/java/com/google/gerrit/server/config/GerritGlobalModule.java
@@ -37,6 +37,7 @@
 import com.google.gerrit.extensions.events.AccountIndexedListener;
 import com.google.gerrit.extensions.events.AgreementSignupListener;
 import com.google.gerrit.extensions.events.AssigneeChangedListener;
+import com.google.gerrit.extensions.events.AttentionSetListener;
 import com.google.gerrit.extensions.events.ChangeAbandonedListener;
 import com.google.gerrit.extensions.events.ChangeDeletedListener;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
@@ -454,6 +455,7 @@
     DynamicSet.setOf(binder(), MailSoyTemplateProvider.class);
     DynamicSet.setOf(binder(), OnPostReview.class);
     DynamicMap.mapOf(binder(), AccountTagProvider.class);
+    DynamicSet.setOf(binder(), AttentionSetListener.class);
 
     DynamicMap.mapOf(binder(), MailFilter.class);
     bind(MailFilter.class).annotatedWith(Exports.named("ListMailFilter")).to(ListMailFilter.class);
diff --git a/java/com/google/gerrit/server/extensions/events/AttentionSetObserver.java b/java/com/google/gerrit/server/extensions/events/AttentionSetObserver.java
new file mode 100644
index 0000000..8f51e13
--- /dev/null
+++ b/java/com/google/gerrit/server/extensions/events/AttentionSetObserver.java
@@ -0,0 +1,112 @@
+// Copyright (C) 2022 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.extensions.events;
+
+import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.entities.AttentionSetUpdate;
+import com.google.gerrit.extensions.api.changes.NotifyHandling;
+import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.events.AttentionSetListener;
+import com.google.gerrit.server.account.AccountCache;
+import com.google.gerrit.server.account.AccountState;
+import com.google.gerrit.server.plugincontext.PluginSetContext;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.time.Instant;
+import java.util.HashSet;
+import java.util.Set;
+
+/** Helper class to fire an event when an attention set changes. */
+@Singleton
+public class AttentionSetObserver {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private final PluginSetContext<AttentionSetListener> listeners;
+  private final EventUtil util;
+  private final AccountCache accountCache;
+
+  @Inject
+  AttentionSetObserver(
+      PluginSetContext<AttentionSetListener> listeners, EventUtil util, AccountCache accountCache) {
+    this.listeners = listeners;
+    this.util = util;
+    this.accountCache = accountCache;
+  }
+
+  /**
+   * Notify all listening plugins
+   *
+   * @param changeData is current data of the change
+   * @param accountState is the initiator of the change
+   * @param update is the update that caused the event
+   * @param when is the time of the event
+   */
+  public void fire(
+      ChangeData changeData, AccountState accountState, AttentionSetUpdate update, Instant when) {
+    if (listeners.isEmpty()) {
+      return;
+    }
+    AccountState target = accountCache.get(update.account()).get();
+
+    HashSet<Integer> added = new HashSet<>();
+    HashSet<Integer> removed = new HashSet<>();
+    switch (update.operation()) {
+      case ADD:
+        added.add(target.account().id().get());
+        break;
+      case REMOVE:
+        removed.add(target.account().id().get());
+        break;
+    }
+
+    try {
+      Event event =
+          new Event(
+              util.changeInfo(changeData), util.accountInfo(accountState), added, removed, when);
+      listeners.runEach(l -> l.onAttentionSetChanged(event));
+    } catch (Exception e) {
+      logger.atSevere().withCause(e).log("Exception while firing AttentionSet changed event");
+    }
+  }
+
+  /** Event to be fired when an attention set changes */
+  private static class Event extends AbstractChangeEvent implements AttentionSetListener.Event {
+    private final Set<Integer> added;
+    private final Set<Integer> removed;
+
+    Event(
+        ChangeInfo change,
+        AccountInfo editor,
+        Set<Integer> added,
+        Set<Integer> removed,
+        Instant when) {
+      super(change, editor, when, NotifyHandling.ALL);
+      this.added = added;
+      this.removed = removed;
+    }
+
+    @Override
+    public Set<Integer> usersAdded() {
+      return added;
+    }
+
+    @Override
+    public Set<Integer> usersRemoved() {
+      return removed;
+    }
+  }
+}
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index c5f0d23..e8ef187 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -83,6 +83,7 @@
 import com.google.gerrit.acceptance.UseClockStep;
 import com.google.gerrit.acceptance.UseTimezone;
 import com.google.gerrit.acceptance.VerifyNoPiiInChangeNotes;
+import com.google.gerrit.acceptance.api.change.ChangeIT.TestAttentionSetListenerModule.TestAttentionSetListener;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
 import com.google.gerrit.acceptance.testsuite.change.IndexOperations;
@@ -147,7 +148,9 @@
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.common.RevisionInfo;
 import com.google.gerrit.extensions.common.TrackingIdInfo;
+import com.google.gerrit.extensions.events.AttentionSetListener;
 import com.google.gerrit.extensions.events.WorkInProgressStateChangedListener;
+import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
@@ -1536,6 +1539,39 @@
   }
 
   @Test
+  public void attentionSetListener_firesOnChange() throws Exception {
+    PushOneCommit.Result r1 = createChange();
+    AttentionSetInput addUser = new AttentionSetInput(user.email(), "some reason");
+    TestAttentionSetListener attentionSetListener = new TestAttentionSetListener();
+
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(attentionSetListener)) {
+
+      gApi.changes().id(r1.getChangeId()).addReviewer(user.email());
+      gApi.changes().id(r1.getChangeId()).addToAttentionSet(addUser);
+
+      assertThat(attentionSetListener.fired).isTrue();
+      assertThat(attentionSetListener.lastEvent.usersAdded().size()).isEqualTo(1);
+      attentionSetListener
+          .lastEvent
+          .usersAdded()
+          .forEach(u -> assertThat(u).isEqualTo(user.id().get()));
+      assertThat(attentionSetListener.lastEvent.usersRemoved()).isEmpty();
+
+      attentionSetListener.fired = false;
+      gApi.changes().id(r1.getChangeId()).attention(user.username()).remove(addUser);
+
+      assertThat(attentionSetListener.fired).isTrue();
+      assertThat(attentionSetListener.lastEvent.usersAdded()).isEmpty();
+      assertThat(attentionSetListener.lastEvent.usersRemoved().size()).isEqualTo(1);
+      attentionSetListener
+          .lastEvent
+          .usersRemoved()
+          .forEach(u -> assertThat(u).isEqualTo(user.id().get()));
+    }
+  }
+
+  @Test
   public void rebaseChangeBase() throws Exception {
     PushOneCommit.Result r1 = createChange();
     PushOneCommit.Result r2 = createChange();
@@ -4752,6 +4788,27 @@
     }
   }
 
+  public static class TestAttentionSetListenerModule extends AbstractModule {
+    @Override
+    public void configure() {
+      DynamicSet.bind(binder(), AttentionSetListener.class).to(TestAttentionSetListener.class);
+    }
+
+    public static class TestAttentionSetListener implements AttentionSetListener {
+      Event lastEvent;
+      boolean fired;
+
+      @Inject
+      public TestAttentionSetListener() {}
+
+      @Override
+      public void onAttentionSetChanged(Event event) {
+        fired = true;
+        lastEvent = event;
+      }
+    }
+  }
+
   private void voteLabel(String changeId, String labelName, int score) throws RestApiException {
     gApi.changes().id(changeId).current().review(new ReviewInput().label(labelName, score));
   }