diff --git a/mobile/lib/presentation/pages/drift_library.page.dart b/mobile/lib/presentation/pages/drift_library.page.dart
index 673df089d5..e93a58be7d 100644
--- a/mobile/lib/presentation/pages/drift_library.page.dart
+++ b/mobile/lib/presentation/pages/drift_library.page.dart
@@ -180,7 +180,11 @@ class _PeopleCollectionCard extends ConsumerWidget {
                       mainAxisSpacing: 8,
                       physics: const NeverScrollableScrollPhysics(),
                       children: people.take(4).map((person) {
-                        return CircleAvatar(backgroundImage: RemoteImageProvider(url: getFaceThumbnailUrl(person.id)));
+                        return CircleAvatar(
+                          backgroundImage: RemoteImageProvider(
+                            url: getFaceThumbnailUrl(person.id, updatedAt: person.updatedAt),
+                          ),
+                        );
                       }).toList(),
                     );
                   },
diff --git a/mobile/lib/presentation/pages/drift_people_collection.page.dart b/mobile/lib/presentation/pages/drift_people_collection.page.dart
index 26aa2e62ab..0afe723dc6 100644
--- a/mobile/lib/presentation/pages/drift_people_collection.page.dart
+++ b/mobile/lib/presentation/pages/drift_people_collection.page.dart
@@ -94,7 +94,9 @@ class _DriftPeopleCollectionPageState extends ConsumerState<DriftPeopleCollectio
                             child: CircleAvatar(
                               key: ValueKey(person.id),
                               maxRadius: isTablet ? 100 / 2 : 96 / 2,
-                              backgroundImage: RemoteImageProvider(url: getFaceThumbnailUrl(person.id)),
+                              backgroundImage: RemoteImageProvider(
+                                url: getFaceThumbnailUrl(person.id, updatedAt: person.updatedAt),
+                              ),
                             ),
                           ),
                         ),
diff --git a/mobile/lib/presentation/widgets/asset_viewer/asset_details/people_details.widget.dart b/mobile/lib/presentation/widgets/asset_viewer/asset_details/people_details.widget.dart
index 32bbc915a1..278da294c0 100644
--- a/mobile/lib/presentation/widgets/asset_viewer/asset_details/people_details.widget.dart
+++ b/mobile/lib/presentation/widgets/asset_viewer/asset_details/people_details.widget.dart
@@ -121,7 +121,9 @@ class _Avatar extends StatelessWidget {
                   elevation: 3,
                   child: CircleAvatar(
                     maxRadius: imageSize / 2,
-                    backgroundImage: RemoteImageProvider(url: getFaceThumbnailUrl(person.id)),
+                    backgroundImage: RemoteImageProvider(
+                      url: getFaceThumbnailUrl(person.id, updatedAt: person.updatedAt),
+                    ),
                   ),
                 ),
               ),
diff --git a/mobile/lib/repositories/person_api.repository.dart b/mobile/lib/repositories/person_api.repository.dart
index 26662601b7..158e3ac333 100644
--- a/mobile/lib/repositories/person_api.repository.dart
+++ b/mobile/lib/repositories/person_api.repository.dart
@@ -32,5 +32,6 @@ class PersonApiRepository extends ApiRepository {
     isHidden: dto.isHidden,
     name: dto.name,
     thumbnailPath: dto.thumbnailPath,
+    updatedAt: dto.updatedAt.orElse(null),
   );
 }
diff --git a/mobile/lib/utils/image_url_builder.dart b/mobile/lib/utils/image_url_builder.dart
index 4635e5ec20..7a7ee03f2b 100644
--- a/mobile/lib/utils/image_url_builder.dart
+++ b/mobile/lib/utils/image_url_builder.dart
@@ -20,6 +20,7 @@ String getPlaybackUrlForRemoteId(final String id) {
   return '${Store.get(StoreKey.serverEndpoint)}/assets/$id/video/playback?';
 }
 
-String getFaceThumbnailUrl(final String personId) {
-  return '${Store.get(StoreKey.serverEndpoint)}/people/$personId/thumbnail';
+String getFaceThumbnailUrl(final String personId, {DateTime? updatedAt}) {
+  final url = '${Store.get(StoreKey.serverEndpoint)}/people/$personId/thumbnail';
+  return updatedAt != null ? '$url?c=${updatedAt.millisecondsSinceEpoch}' : url;
 }
diff --git a/mobile/lib/widgets/common/person_sliver_app_bar.dart b/mobile/lib/widgets/common/person_sliver_app_bar.dart
index 34ffcb2ad8..a9f9413c47 100644
--- a/mobile/lib/widgets/common/person_sliver_app_bar.dart
+++ b/mobile/lib/widgets/common/person_sliver_app_bar.dart
@@ -230,7 +230,9 @@ class _ExpandedBackgroundState extends ConsumerState<_ExpandedBackground> with S
                     elevation: 3,
                     child: CircleAvatar(
                       maxRadius: 84 / 2,
-                      backgroundImage: RemoteImageProvider(url: getFaceThumbnailUrl(widget.person.id)),
+                      backgroundImage: RemoteImageProvider(
+                        url: getFaceThumbnailUrl(widget.person.id, updatedAt: widget.person.updatedAt),
+                      ),
                     ),
                   ),
                 ),
diff --git a/mobile/lib/widgets/search/search_filter/people_picker.dart b/mobile/lib/widgets/search/search_filter/people_picker.dart
index 24b625e95e..a9382ec3ae 100644
--- a/mobile/lib/widgets/search/search_filter/people_picker.dart
+++ b/mobile/lib/widgets/search/search_filter/people_picker.dart
@@ -80,7 +80,9 @@ class PeoplePicker extends HookConsumerWidget {
                           child: CircleAvatar(
                             key: ValueKey(person.id),
                             maxRadius: imageSize / 2,
-                            backgroundImage: RemoteImageProvider(url: getFaceThumbnailUrl(person.id)),
+                            backgroundImage: RemoteImageProvider(
+                              url: getFaceThumbnailUrl(person.id, updatedAt: person.updatedAt),
+                            ),
                           ),
                         ),
                       ),
diff --git a/mobile/test/utils/image_url_builder_test.dart b/mobile/test/utils/image_url_builder_test.dart
new file mode 100644
index 0000000000..1845d38eeb
--- /dev/null
+++ b/mobile/test/utils/image_url_builder_test.dart
@@ -0,0 +1,35 @@
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/domain/models/store.model.dart';
+import 'package:immich_mobile/domain/services/store.service.dart';
+import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
+import 'package:immich_mobile/infrastructure/repositories/store.repository.dart';
+import 'package:immich_mobile/utils/image_url_builder.dart';
+
+void main() {
+  const endpoint = 'http://localhost:3000';
+
+  setUpAll(() async {
+    final db = Drift(DatabaseConnection(NativeDatabase.memory(), closeStreamsSynchronously: true));
+    await StoreService.init(storeRepository: DriftStoreRepository(db), listenUpdates: false);
+    await StoreService.I.put(StoreKey.serverEndpoint, endpoint);
+  });
+
+  group('getFaceThumbnailUrl', () {
+    test('omits the cache buster when updatedAt is null', () {
+      expect(getFaceThumbnailUrl('person-1'), '$endpoint/people/person-1/thumbnail');
+    });
+
+    test('appends the updatedAt cache buster so a changed featured photo busts the cache (#27434)', () {
+      final url = getFaceThumbnailUrl('person-1', updatedAt: DateTime.fromMillisecondsSinceEpoch(1717000000000));
+      expect(url, '$endpoint/people/person-1/thumbnail?c=1717000000000');
+    });
+
+    test('a newer updatedAt yields a different url so the image cache key changes', () {
+      final before = getFaceThumbnailUrl('person-1', updatedAt: DateTime.fromMillisecondsSinceEpoch(1));
+      final after = getFaceThumbnailUrl('person-1', updatedAt: DateTime.fromMillisecondsSinceEpoch(2));
+      expect(before, isNot(after));
+    });
+  });
+}