diff --git a/packages/ui-drilldown/src/Drilldown/index.tsx b/packages/ui-drilldown/src/Drilldown/index.tsx
index 2e0bd01f8b..725ea55850 100644
--- a/packages/ui-drilldown/src/Drilldown/index.tsx
+++ b/packages/ui-drilldown/src/Drilldown/index.tsx
@@ -887,8 +887,20 @@ class Drilldown extends Component<DrilldownProps, DrilldownState> {
   }
 
   handleToggle = (event: React.UIEvent | React.FocusEvent, shown: boolean) => {
-    const { onToggle } = this.props
-
+    const { onToggle, trigger } = this.props
+
+    if (trigger && shown && this.currentPage) {
+      const actionLabel = callRenderProp(this.currentPage.renderActionLabel)
+      // Use action ID if exists, otherwise first non-action option's ID
+      const targetId = actionLabel
+        ? this._headerActionId
+        : this.currentPage.children[0]?.props.id
+      setTimeout(() => {
+        this.setState({
+          highlightedOptionId: targetId
+        })
+      }, 10)
+    }
     this.setState({ isShowingPopover: shown })
 
     if (typeof onToggle === 'function') {
@@ -1481,7 +1493,7 @@ class Drilldown extends Component<DrilldownProps, DrilldownState> {
           this.handleToggle(event, false)
         }}
         onShowContent={(event) => this.handleToggle(event, true)}
-        mountNode={mountNode}
+        mountNode={mountNode || this.ref}
         placement={placement}
         withArrow={withArrow}
         positionTarget={positionTarget}
@@ -1495,6 +1507,17 @@ class Drilldown extends Component<DrilldownProps, DrilldownState> {
         onMouseOver={onMouseOver}
         offsetX={offsetX}
         offsetY={offsetY}
+        defaultFocusElement={() => {
+          if (!this.currentPage) return null
+          const actionLabel = callRenderProp(this.currentPage.renderActionLabel)
+          // Use action ID if exists, otherwise first non-action option's ID
+          const targetId = actionLabel
+            ? this._headerActionId
+            : this.currentPage.children[0]?.props.id
+
+          if (!targetId) return null
+          return this._popover?._contentElement?.querySelector(`#${targetId}`)
+        }}
         elementRef={(element) => {
           // setting ref for "Popover" version, the popover root
           // (if there is no trigger, we set it in handleDrilldownRef)
diff --git a/packages/ui-drilldown/src/Drilldown/props.ts b/packages/ui-drilldown/src/Drilldown/props.ts
index 2931127ca3..0dbf36f924 100644
--- a/packages/ui-drilldown/src/Drilldown/props.ts
+++ b/packages/ui-drilldown/src/Drilldown/props.ts
@@ -207,7 +207,7 @@ type DrilldownOwnProps = {
 
   /**
    * If a trigger is supplied, an element or a function returning an element
-   * to use as the mount node for the `<Drilldown />` (defaults to `document.body`)
+   * to use as the mount node for the `<Drilldown />` (defaults to the component itself)
    */
   mountNode?: PositionMountNode
 
diff --git a/packages/ui-top-nav-bar/src/TopNavBar/README.md b/packages/ui-top-nav-bar/src/TopNavBar/README.md
index b1f6aa0842..465783aa49 100644
--- a/packages/ui-top-nav-bar/src/TopNavBar/README.md
+++ b/packages/ui-top-nav-bar/src/TopNavBar/README.md
@@ -648,12 +648,10 @@ class PlaygroundExample extends React.Component {
 
                       {...item.submenu && {
                         renderSubmenu: this.generateSubmenu(item),
-                        'aria-label': `Open for ${item.label} menu`
                       }}
 
                       {...item.customPopoverConfig && {
                         customPopoverConfig: item.customPopoverConfig,
-                        'aria-label': `Open for ${item.label} menu`
                       }}
 
                       {...!item.submenu && !item.customPopoverConfig ? {
@@ -720,7 +718,7 @@ class PlaygroundExample extends React.Component {
                   <TopNavBar.Item
                     id="Info"
                     renderIcon={<IconQuestionLine />}
-                    aria-label="Open for info menu"
+                    aria-label="info menu"
                     renderSubmenu={this.generateSubmenu({
                       id: 'Info',
                       submenu: ['Contact', 'Map', 'Career'].map(item => ({
diff --git a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/DesktopLayout/styles.ts b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/DesktopLayout/styles.ts
index fe9c0d50a6..71c20bf117 100644
--- a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/DesktopLayout/styles.ts
+++ b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/DesktopLayout/styles.ts
@@ -66,10 +66,9 @@ const generateStyle = (
       alignItems: 'stretch',
       justifyContent: 'space-between',
       height: componentTheme.desktopHeight,
-      position: 'relative',
       zIndex: componentTheme.desktopZIndex,
       maxWidth: '100%',
-      overflow: 'hidden',
+      overflow: 'visible',
       paddingInline: componentTheme.desktopInlinePadding,
       paddingBlock: 0,
       ...(hasBrandBlock && {
@@ -113,7 +112,6 @@ const generateStyle = (
       marginInline: componentTheme.desktopUserContainerInlineMargin,
 
       ...(hasUserSeparator && {
-        position: 'relative',
         paddingInlineStart: componentTheme.desktopUserSeparatorGap,
 
         '&::before': {
diff --git a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/SmallViewportLayout/index.tsx b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/SmallViewportLayout/index.tsx
index 06ac0b5edf..96c811f36c 100644
--- a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/SmallViewportLayout/index.tsx
+++ b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarLayout/SmallViewportLayout/index.tsx
@@ -104,6 +104,7 @@ class TopNavBarSmallViewportLayout extends Component<
   private readonly _inPlaceDialogId: string
   private readonly _inPlaceDialogCloseButtonId: string
   private readonly _separatorId: string
+  private _drilldownRef: Drilldown | null = null
 
   private _raf: RequestAnimationFrameType[] = []
 
@@ -286,7 +287,44 @@ class TopNavBarSmallViewportLayout extends Component<
       onDropdownMenuToggle(!isDropdownMenuOpen)
     }
 
-    this.setState({ isDropdownMenuOpen: !isDropdownMenuOpen })
+    this.setState(
+      { isDropdownMenuOpen: !this.state.isDropdownMenuOpen },
+      () => {
+        if (this.state.isDropdownMenuOpen) {
+          this.focusFirstAvailableItem()
+        }
+      }
+    )
+  }
+
+  focusFirstAvailableItem() {
+    const userChildren = Children.toArray(
+      this.props.renderUser?.props.children
+    ) as ItemChild[]
+
+    // If option is a User, it preceeds other item, so focus that first
+    const targetId = userChildren[0]
+      ? userChildren[0].props.id
+      : this.mappedMenuItemsOptions[0].optionData.id
+
+    setTimeout(() => {
+      const container = document.getElementById(this._trayContainerId)
+      const firstOption = container?.querySelector(
+        `[id="${targetId}"]`
+      ) as HTMLSpanElement
+      firstOption?.focus()
+      if (this._drilldownRef) {
+        const drilldownRef = this._drilldownRef
+        setTimeout(() => {
+          if (drilldownRef) {
+            // highlight the option using Drilldown's handleOptionHighlight function
+            drilldownRef.handleOptionHighlight({} as React.SyntheticEvent, {
+              id: targetId
+            })
+          }
+        }, 10)
+      }
+    }, 10)
   }
 
   renderOptionContent: RenderOptionContent = (children, itemProps) => {
@@ -402,6 +440,9 @@ class TopNavBarSmallViewportLayout extends Component<
     return (
       <div css={styles?.menuTriggerContainer}>
         {menuTrigger}
+        {!this.hasBreadcrumbBlock && !this.props.trayMountNode && (
+          <div css={styles?.trayContainer} id={this._trayContainerId} />
+        )}
 
         {this.hasBrandBlock(renderBrand) && !alternativeTitle && (
           <div css={styles?.brandContainer}>{renderBrand}</div>
@@ -442,6 +483,9 @@ class TopNavBarSmallViewportLayout extends Component<
 
     return (
       <Drilldown
+        ref={(el) => {
+          this._drilldownRef = el
+        }}
         id={this._drilldownId}
         rootPageId={this._menuId}
         label={dropdownMenuLabel}
@@ -576,13 +620,7 @@ class TopNavBarSmallViewportLayout extends Component<
   }
 
   render() {
-    const {
-      trayMountNode,
-      navLabel,
-      renderActionItems,
-      renderBreadcrumb,
-      styles
-    } = this.props
+    const { navLabel, renderActionItems, renderBreadcrumb, styles } = this.props
 
     return (
       <nav
@@ -607,10 +645,6 @@ class TopNavBarSmallViewportLayout extends Component<
 
         {!this.hasBreadcrumbBlock && this.renderInPlaceDialog()}
 
-        {!this.hasBreadcrumbBlock && !trayMountNode && (
-          <div css={styles?.trayContainer} id={this._trayContainerId} />
-        )}
-
         {!this.hasBreadcrumbBlock && this.renderDropdownMenuTray()}
       </nav>
     )
diff --git a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarMenuItems/styles.ts b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarMenuItems/styles.ts
index 043882d90b..64c3cba1f8 100644
--- a/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarMenuItems/styles.ts
+++ b/packages/ui-top-nav-bar/src/TopNavBar/TopNavBarMenuItems/styles.ts
@@ -51,7 +51,8 @@ const generateStyle = (
       flexDirection: 'row',
       alignItems: 'stretch',
       // padding to prevent focus ring getting cropped by `overflow: hidden`
-      padding: '0 0.125rem'
+      padding: '0 0.125rem',
+      overflow: 'visible'
     },
     submenuOption: {
       label: 'topNavBarMenuItems__submenuOption',