diff --git a/.changeset/fast-pots-say.md b/.changeset/fast-pots-say.md
new file mode 100644
index 00000000000..3b4a1f51029
--- /dev/null
+++ b/.changeset/fast-pots-say.md
@@ -0,0 +1,5 @@
+---
+'@primer/react': patch
+---
+
+ActionMenu: Ensures that uncontrolled ActionMenu(s) retain tab-focus when fullscreen
diff --git a/packages/react/src/ActionMenu/ActionMenu.tsx b/packages/react/src/ActionMenu/ActionMenu.tsx
index 7ed22316759..7e97ae4d673 100644
--- a/packages/react/src/ActionMenu/ActionMenu.tsx
+++ b/packages/react/src/ActionMenu/ActionMenu.tsx
@@ -285,12 +285,25 @@ const Overlay: FCWithSlotMarker<React.PropsWithChildren<MenuOverlayProps>> = ({
   } = React.useContext(MenuContext) as MandateProps<MenuContextProps, 'anchorRef'>
 
   const containerRef = React.useRef<HTMLDivElement>(null)
-  useMenuKeyboardNavigation(open, onClose, containerRef, anchorRef, isSubmenu)
   const isNarrow = useResponsiveValue({narrow: true}, false)
-  const responsiveVariant = useResponsiveValue(variant, {regular: 'anchored', narrow: 'anchored'})
 
   const isNarrowFullscreen = !!isNarrow && variant.narrow === 'fullscreen'
 
+  const handleClose: MenuCloseHandler = React.useCallback(
+    gesture => {
+      // In narrow fullscreen mode, don't close on tab, let focus stay in the menu
+      if (isNarrowFullscreen && gesture === 'tab') {
+        return
+      }
+      onClose?.(gesture)
+    },
+    [isNarrowFullscreen, onClose],
+  )
+
+  useMenuKeyboardNavigation(open, handleClose, containerRef, anchorRef, isSubmenu)
+
+  const responsiveVariant = useResponsiveValue(variant, {regular: 'anchored', narrow: 'anchored'})
+
   // If the menu anchor is an icon button, we need to label the menu by tooltip that also labelled the anchor.
   const [anchorAriaLabelledby, setAnchorAriaLabelledby] = useState<null | string>(null)
   useEffect(() => {
@@ -311,7 +324,7 @@ const Overlay: FCWithSlotMarker<React.PropsWithChildren<MenuOverlayProps>> = ({
       anchorId={anchorId}
       open={open}
       onOpen={onOpen}
-      onClose={onClose}
+      onClose={handleClose}
       align={align}
       side={side ?? (isSubmenu ? 'outside-right' : 'outside-bottom')}
       overlayProps={overlayProps}