Index: src/js/_enqueues/lib/admin-bar.js
===================================================================
--- src/js/_enqueues/lib/admin-bar.js	(revision 48079)
+++ src/js/_enqueues/lib/admin-bar.js	(working copy)
@@ -13,6 +13,9 @@
  * @return {void}
  */
 ( function( document, window, navigator ) {
+	var adminBarMyAccount,
+		adminBarMyAccountLink;
+
 	document.addEventListener( 'DOMContentLoaded', function() {
 		var adminBar = document.getElementById( 'wpadminbar' ),
 			topMenuItems,
@@ -33,6 +36,8 @@
 		allMenuItems = adminBar.querySelectorAll( '.ab-item' );
 		adminBarLogout = document.getElementById( 'wp-admin-bar-logout' );
 		adminBarSearchForm = document.getElementById( 'adminbarsearch' );
+		adminBarMyAccount = document.getElementById( 'wp-admin-bar-my-account' );
+		adminBarMyAccountLink = document.querySelector( '#wp-admin-bar-my-account > .ab-item');
 		shortlink = document.getElementById( 'wp-admin-bar-get-shortlink' );
 		skipLink = adminBar.querySelector( '.screen-reader-shortcut' );
 		mobileEvent = /Mobile\/.+Safari/.test( navigator.userAgent ) ? 'touchstart' : 'click';
@@ -56,6 +61,8 @@
 				}
 
 				adminBar.removeEventListener( 'touchstart', bindMobileEvents );
+				adminBarMyAccountLink.removeEventListener( 'click', toggleMyAccount );
+				adminBarMyAccountLink.removeEventListener( 'keyup', toggleMyAccountViaKeyboard );
 			} );
 		}
 
@@ -63,22 +70,32 @@
 		adminBar.addEventListener( 'click', scrollToTop );
 
 		for ( i = 0; i < topMenuItems.length; i++ ) {
-			// Adds or removes the hover class based on the hover intent.
-			window.hoverintent(
-				topMenuItems[i],
-				addClass.bind( null, topMenuItems[i], 'hover' ),
-				removeClass.bind( null, topMenuItems[i], 'hover' )
-			).options( {
-				timeout: 180
-			} );
+			if ( topMenuItems[i].id !== 'wp-admin-bar-my-account' ) {
+				// Adds or removes the hover class based on the hover intent, except for My Account menu.
+				window.hoverintent(
+					topMenuItems[i],
+					addClass.bind( null, topMenuItems[i], 'hover' ),
+					removeClass.bind( null, topMenuItems[i], 'hover' )
+				).options( {
+					timeout: 180
+				} );
 
-			// Toggle hover class if the enter key is pressed.
-			topMenuItems[i].addEventListener( 'keydown', toggleHoverIfEnter );
+				// Toggle hover class if the enter key is pressed.
+				topMenuItems[i].addEventListener( 'keydown', toggleHoverIfEnter );
+			}
 		}
 
+		// Toggle the My Account menu on click.
+		adminBarMyAccountLink.addEventListener( 'click', toggleMyAccount );
+
+		// Make the My Account menu link be perceived and behave as a button.
+		adminBarMyAccountLink.addEventListener( 'keyup', toggleMyAccountViaKeyboard );
+		adminBarMyAccountLink.setAttribute( 'role', 'button' );
+		adminBarMyAccountLink.setAttribute( 'aria-expanded', 'false' );
+
 		// Remove hover class if the escape key is pressed.
 		for ( i = 0; i < allMenuItems.length; i++ ) {
-			allMenuItems[i].addEventListener( 'keydown', removeHoverIfEscape );
+			allMenuItems[i].addEventListener( 'keydown', handleKeyDown );
 		}
 
 		if ( adminBarSearchForm ) {
@@ -113,30 +130,83 @@
 		if ( adminBarLogout ) {
 			adminBarLogout.addEventListener( 'click', emptySessionStorage );
 		}
+
+		/**
+		 * Toggles the My Account menu on the click event.
+		 *
+		 * @since 5.5.0
+		 *
+		 * @param {Event} event The click event.
+		 */
+		function toggleMyAccount( event ) {
+			event.preventDefault();
+			adminBarMyAccount.classList.toggle( 'hover' );
+			updateMyAccountAriaExpanded();
+		}
+
+		/**
+		 * Toggles the My Account menu when pressing the Spacebar key.
+		 *
+		 * @since 5.5.0
+		 *
+		 * @param {Event} event The keyup event.
+		 */
+		function toggleMyAccountViaKeyboard( event ) {
+			if ( event.which !== 32 ) {
+				return;
+			}
+
+			adminBarMyAccount.classList.toggle( 'hover' );
+			updateMyAccountAriaExpanded();
+		}
 	} );
 
 	/**
-	 * Remove hover class for top level menu item when escape is pressed.
+	 * Updates the My Account menu aria-expanded attribute.
 	 *
+	 * @since 5.5.0
+	 */
+	function updateMyAccountAriaExpanded() {
+		if ( hasClass( adminBarMyAccount, 'hover' ) ) {
+			adminBarMyAccountLink.setAttribute( 'aria-expanded', 'true' );
+			return;
+		}
+
+		adminBarMyAccountLink.setAttribute( 'aria-expanded', 'false' );
+	}
+
+	/**
+	 * Handles the keydown event on the menu items.
+	 *
 	 * @since 5.3.1
 	 *
 	 * @param {Event} event The keydown event.
 	 */
-	function removeHoverIfEscape( event ) {
-		var wrapper;
+	function handleKeyDown( event ) {
+		var wrapper = getClosest( event.target, '.menupop' );
 
-		if ( event.which !== 27 ) {
+		if ( ! wrapper ) {
 			return;
 		}
 
-		wrapper = getClosest( event.target, '.menupop' );
+		// Prevent scrolling the page when activating the My Account link via the Spacebar key.
+		if ( event.which === 32 && wrapper.id === 'wp-admin-bar-my-account' ) {
+			event.preventDefault();
+		}
 
-		if ( ! wrapper ) {
+		if ( event.which !== 27 ) {
 			return;
 		}
 
+		// Close a menu when the Escape key is pressed.
+		removeClass( wrapper, 'hover' );
+		// Move focus to the menu top item link.
 		wrapper.querySelector( '.menupop > .ab-item' ).focus();
-		removeClass( wrapper, 'hover' );
+
+		// Update the My Account link aria-expanded attribute.
+		if ( wrapper.id === 'wp-admin-bar-my-account' ) {
+			updateMyAccountAriaExpanded();
+		}
 	}
 
 	/**
Index: src/wp-includes/admin-bar.php
===================================================================
--- src/wp-includes/admin-bar.php	(revision 48079)
+++ src/wp-includes/admin-bar.php	(working copy)
@@ -245,12 +245,13 @@
 	/* translators: %s: Current user's display name. */
 	$howdy = sprintf( __( 'Howdy, %s' ), '<span class="display-name">' . $current_user->display_name . '</span>' );
 	$class = empty( $avatar ) ? '' : 'with-avatar';
+	$icon  = '<span class="my-account-toggle-indicator hide-if-no-js" aria-hidden="true"></span>';
 
 	$wp_admin_bar->add_node(
 		array(
 			'id'     => 'my-account',
 			'parent' => 'top-secondary',
-			'title'  => $howdy . $avatar,
+			'title'  => $icon . $howdy . $avatar,
 			'href'   => $profile_url,
 			'meta'   => array(
 				'class' => $class,
Index: src/wp-includes/css/admin-bar.css
===================================================================
--- src/wp-includes/css/admin-bar.css	(revision 48079)
+++ src/wp-includes/css/admin-bar.css	(working copy)
@@ -399,6 +399,29 @@
 	min-width: 198px;
 }
 
+#wp-admin-bar-my-account .my-account-toggle-indicator {
+	display: inline-flex;
+	align-items: center;
+	height: 32px;
+	margin-right: 5px;
+	vertical-align: top;
+}
+
+#wp-admin-bar-my-account .my-account-toggle-indicator:before {
+	content: "\f347";
+	font: normal 20px/1 dashicons;
+	speak: none;
+	display: inline-block;
+	-webkit-font-smoothing: antialiased;
+	-moz-osx-font-smoothing: grayscale;
+	text-decoration: none !important;
+	color: currentColor;
+}
+
+#wp-admin-bar-my-account.hover .my-account-toggle-indicator:before {
+	content: "\f343";
+}
+
 #wp-admin-bar-my-account > .ab-item:before {
 	content: "\f110";
 	top: 2px;