diff --git a/i18n/en.json b/i18n/en.json
index e86b56be85..bd59c37fac 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -33,6 +33,7 @@
   "add_to_albums": "Add to albums",
   "add_to_albums_count": "Add to albums ({count})",
   "add_to_shared_album": "Add to shared album",
+  "add_upload_to_stack": "Add upload to stack",
   "add_url": "Add URL",
   "added_to_archive": "Added to archive",
   "added_to_favorites": "Added to favorites",
diff --git a/web/src/lib/components/asset-viewer/actions/action.ts b/web/src/lib/components/asset-viewer/actions/action.ts
index 680dced7ca..6a807d2766 100644
--- a/web/src/lib/components/asset-viewer/actions/action.ts
+++ b/web/src/lib/components/asset-viewer/actions/action.ts
@@ -12,6 +12,7 @@ type ActionMap = {
   [AssetAction.RESTORE]: { asset: TimelineAsset };
   [AssetAction.ADD]: { asset: TimelineAsset };
   [AssetAction.ADD_TO_ALBUM]: { asset: TimelineAsset; album: AlbumResponseDto };
+  [AssetAction.STACK]: { stack: StackResponseDto };
   [AssetAction.UNSTACK]: { assets: TimelineAsset[] };
   [AssetAction.KEEP_THIS_DELETE_OTHERS]: { asset: TimelineAsset };
   [AssetAction.SET_STACK_PRIMARY_ASSET]: { stack: StackResponseDto };
diff --git a/web/src/lib/components/asset-viewer/actions/add-to-stack-action.svelte b/web/src/lib/components/asset-viewer/actions/add-to-stack-action.svelte
new file mode 100644
index 0000000000..5b30beff6e
--- /dev/null
+++ b/web/src/lib/components/asset-viewer/actions/add-to-stack-action.svelte
@@ -0,0 +1,37 @@
+<script lang="ts">
+  import MenuOption from '$lib/components/shared-components/context-menu/menu-option.svelte';
+  import { AssetAction } from '$lib/constants';
+  import { openFileUploadDialog } from '$lib/utils/file-uploader';
+  import { createStack, type AssetResponseDto, type StackResponseDto } from '@immich/sdk';
+  import { mdiUploadMultiple } from '@mdi/js';
+  import { t } from 'svelte-i18n';
+  import type { OnAction } from './action';
+
+  interface Props {
+    asset: AssetResponseDto;
+    stack: StackResponseDto | null;
+    onAction: OnAction;
+  }
+
+  let { asset, stack, onAction }: Props = $props();
+
+  const handleAddUploadToStack = async () => {
+    const newAssetIds = await openFileUploadDialog({ multiple: true });
+    // Including the old stacks primary asset ID ensures that all assets of the
+    // old stack are automatically included in the new stack.
+    const primaryAssetId = stack?.primaryAssetId ?? asset.id;
+
+    // First asset in the list will become the new primary asset.
+    const assetIds = [primaryAssetId, ...newAssetIds];
+
+    const newStack = await createStack({
+      stackCreateDto: {
+        assetIds,
+      },
+    });
+
+    onAction({ type: AssetAction.STACK, stack: newStack });
+  };
+</script>
+
+<MenuOption icon={mdiUploadMultiple} onClick={handleAddUploadToStack} text={$t('add_upload_to_stack')} />
diff --git a/web/src/lib/components/asset-viewer/asset-viewer-nav-bar.svelte b/web/src/lib/components/asset-viewer/asset-viewer-nav-bar.svelte
index bbdd0dcd5f..d61af04db6 100644
--- a/web/src/lib/components/asset-viewer/asset-viewer-nav-bar.svelte
+++ b/web/src/lib/components/asset-viewer/asset-viewer-nav-bar.svelte
@@ -4,6 +4,7 @@
   import CastButton from '$lib/cast/cast-button.svelte';
   import type { OnAction, PreAction } from '$lib/components/asset-viewer/actions/action';
   import AddToAlbumAction from '$lib/components/asset-viewer/actions/add-to-album-action.svelte';
+  import AddToStackAction from '$lib/components/asset-viewer/actions/add-to-stack-action.svelte';
   import ArchiveAction from '$lib/components/asset-viewer/actions/archive-action.svelte';
   import CloseAction from '$lib/components/asset-viewer/actions/close-action.svelte';
   import DeleteAction from '$lib/components/asset-viewer/actions/delete-action.svelte';
@@ -196,6 +197,7 @@
         {/if}
 
         {#if isOwner}
+          <AddToStackAction {asset} {stack} {onAction} />
           {#if stack}
             <UnstackAction {stack} {onAction} />
             <KeepThisDeleteOthersAction {stack} {asset} {onAction} />
diff --git a/web/src/lib/components/asset-viewer/asset-viewer.svelte b/web/src/lib/components/asset-viewer/asset-viewer.svelte
index 5484cd2c08..3dd7741af5 100644
--- a/web/src/lib/components/asset-viewer/asset-viewer.svelte
+++ b/web/src/lib/components/asset-viewer/asset-viewer.svelte
@@ -336,6 +336,7 @@
         }
         break;
       }
+      case AssetAction.STACK:
       case AssetAction.SET_STACK_PRIMARY_ASSET: {
         stack = action.stack;
         break;
diff --git a/web/src/lib/components/timeline/TimelineAssetViewer.svelte b/web/src/lib/components/timeline/TimelineAssetViewer.svelte
index 17e3ed06f3..60b839d7e1 100644
--- a/web/src/lib/components/timeline/TimelineAssetViewer.svelte
+++ b/web/src/lib/components/timeline/TimelineAssetViewer.svelte
@@ -120,6 +120,16 @@
         break;
       }
 
+      case AssetAction.STACK: {
+        updateStackedAssetInTimeline(timelineManager, {
+          stack: action.stack,
+          toDeleteIds: action.stack.assets
+            .filter((asset) => asset.id !== action.stack.primaryAssetId)
+            .map((asset) => asset.id),
+        });
+        break;
+      }
+
       case AssetAction.UNSTACK: {
         updateUnstackedAssetInTimeline(timelineManager, action.assets);
         break;
diff --git a/web/src/lib/constants.ts b/web/src/lib/constants.ts
index da638bb41d..8d2b706ead 100644
--- a/web/src/lib/constants.ts
+++ b/web/src/lib/constants.ts
@@ -8,6 +8,7 @@ export enum AssetAction {
   RESTORE = 'restore',
   ADD = 'add',
   ADD_TO_ALBUM = 'add-to-album',
+  STACK = 'stack',
   UNSTACK = 'unstack',
   KEEP_THIS_DELETE_OTHERS = 'keep-this-delete-others',
   SET_STACK_PRIMARY_ASSET = 'set-stack-primary-asset',
diff --git a/web/src/lib/utils/file-uploader.ts b/web/src/lib/utils/file-uploader.ts
index c572ec1760..3f602bdb29 100644
--- a/web/src/lib/utils/file-uploader.ts
+++ b/web/src/lib/utils/file-uploader.ts
@@ -52,7 +52,7 @@ export const openFileUploadDialog = async (options: FileUploadParam = {}) => {
   const { albumId, multiple = true, assetId } = options;
   const extensions = uploadManager.getExtensions();
 
-  return new Promise<(string | undefined)[]>((resolve, reject) => {
+  return new Promise<string[]>((resolve, reject) => {
     try {
       const fileSelector = document.createElement('input');