Index: src/wp-admin/css/common.css
===================================================================
--- src/wp-admin/css/common.css	(revision 33934)
+++ src/wp-admin/css/common.css	(working copy)
@@ -1786,13 +1786,15 @@
 }
 
 .postbox .handlediv {
+	display: none;
 	float: right;
-	width: 33px;
+	width: 36px;
 	height: 36px;
+	padding: 0;
 }
 
 .js .postbox .handlediv {
-	cursor: pointer;
+	display: block;
 }
 
 .sortable-placeholder {
@@ -2725,19 +2727,23 @@
 
 /* Metabox collapse arrow indicators */
 .js .sidebar-name .sidebar-name-arrow:before,
-.js .meta-box-sortables .postbox .handlediv:before {
-	right: 12px;
+.js .meta-box-sortables .postbox .toggle-indicator:before {
+	position: relative;
+	left: -1px; /* fix the dashicon horizontal alignment */
+	display: inline-block;
 	font: normal 20px/1 dashicons;
 	speak: none;
-	display: inline-block;
-	padding: 8px 10px;
-	top: 0;
-	position: relative;
+	padding: 8px;
 	-webkit-font-smoothing: antialiased;
 	-moz-osx-font-smoothing: grayscale;
 	text-decoration: none !important;
 }
 
+.js .sidebar-name .sidebar-name-arrow:before {
+	padding: 10px;
+	left: 0;
+}
+
 .js #widgets-left .sidebar-name .sidebar-name-arrow {
 	display: none;
 }
@@ -2749,12 +2755,12 @@
 
 /* Show the arrow only on hover */
 .js .sidebar-name .sidebar-name-arrow:before,
-.js .meta-box-sortables .postbox .handlediv:before {
+.js .meta-box-sortables .postbox .toggle-indicator:before {
 	content: '\f142';
 }
 
 .js .widgets-holder-wrap.closed .sidebar-name-arrow:before,
-.js .meta-box-sortables .postbox.closed .handlediv:before {
+.js .meta-box-sortables .postbox.closed .handlediv .toggle-indicator:before {
 	content: '\f140';
 }
 
@@ -2889,6 +2895,7 @@
 
 .widget-action:hover,
 .handlediv:hover,
+.handlediv:focus,
 .item-edit:hover,
 .sidebar-name:hover .sidebar-name-arrow,
 .accordion-section-title:hover:after {
Index: src/wp-admin/css/widgets.css
===================================================================
--- src/wp-admin/css/widgets.css	(revision 33934)
+++ src/wp-admin/css/widgets.css	(working copy)
@@ -147,10 +147,8 @@
 	margin: 0 10px 0 0;
 }
 
-div#widgets-left .sidebar-name .sidebar-name-arrow:before {
-	right: 0;
-	top: 4px;
-	padding: 4px 6px 4px 4px;
+#widgets-left .sidebar-name .sidebar-name-arrow:before {
+	padding: 9px;
 }
 
 #widgets-left #available-widgets,
@@ -250,8 +248,7 @@
 }
 
 div#widgets-right .sidebar-name .sidebar-name-arrow:before {
-	right: 0;
-	top: 4px;
+	top: 2px;
 }
 
 div#widgets-right .widget-top {
Index: src/wp-admin/includes/template.php
===================================================================
--- src/wp-admin/includes/template.php	(revision 33934)
+++ src/wp-admin/includes/template.php	(working copy)
@@ -1096,8 +1096,9 @@
 					$hidden_class = in_array($box['id'], $hidden) ? ' hide-if-js' : '';
 					echo '<div id="' . $box['id'] . '" class="postbox ' . postbox_classes($box['id'], $page) . $hidden_class . '" ' . '>' . "\n";
 					if ( 'dashboard_browser_nag' != $box['id'] ) {
-						echo '<button class="handlediv button-link" title="' . esc_attr__( 'Click to toggle' ) . '" aria-expanded="true">';
-						echo '<span class="screen-reader-text">' . sprintf( __( 'Click to toggle %s panel' ), $box['title'] ) . '</span><br />';
+						echo '<button type="button" class="handlediv button-link" aria-expanded="true">';
+						echo '<span class="screen-reader-text">' . sprintf( __( 'Toggle panel: %s' ), $box['title'] ) . '</span>';
+						echo '<span class="toggle-indicator" aria-hidden="true"></span>';
 						echo '</button>';
 					}
 					echo "<h3 class='hndle'><span>{$box['title']}</span></h3>\n";
Index: src/wp-admin/js/postbox.js
===================================================================
--- src/wp-admin/js/postbox.js	(revision 33934)
+++ src/wp-admin/js/postbox.js	(working copy)
@@ -7,21 +7,31 @@
 
 	postboxes = {
 		add_postbox_toggles : function(page, args) {
-			var self = this;
+			var self = this,
+				$handles = $( '.postbox .hndle, .postbox .handlediv' );
 
 			self.init(page, args);
 
-			$('.postbox .hndle, .postbox .handlediv').bind('click.postboxes', function( e ) {
-				var p = $(this).parent('.postbox'), id = p.attr('id');
+			$handles.on( 'click.postboxes', function() {
+				var p = $( this ).parent( '.postbox' ),
+					id = p.attr( 'id' ),
+					ariaExpandedValue;
 
 				if ( 'dashboard_browser_nag' == id )
 					return;
 
-				e.preventDefault();
-
 				p.toggleClass( 'closed' );
-				$(this).attr( 'aria-expanded', ! p.hasClass( 'closed' ) );
 
+				ariaExpandedValue = ! p.hasClass( 'closed' );
+
+				if ( $( this ).hasClass( 'handlediv' ) ) {
+					// The handle button was clicked.
+					$( this ).attr( 'aria-expanded', ariaExpandedValue );
+				} else {
+					// The handle heading was clicked.
+					$( this ).closest( '.postbox' ).find( 'button.handlediv' ).attr( 'aria-expanded', ariaExpandedValue );
+				}
+
 				if ( page != 'press-this' )
 					self.save_state(page);
 
@@ -74,7 +84,8 @@
 		},
 
 		init : function(page, args) {
-			var isMobile = $(document.body).hasClass('mobile');
+			var isMobile = $( document.body ).hasClass( 'mobile' ),
+				$handleButtons = $( '.postbox .handlediv' );
 
 			$.extend( this, args || {} );
 			$('#wpbody-content').css('overflow','hidden');
@@ -112,6 +123,12 @@
 			}
 
 			this._mark_area();
+
+			// Set the `aria-expanded` handle buttons attribute on page load.
+			$handleButtons.each( function() {
+				var p = $( this ).parent( '.postbox' );
+				$( this ).attr( 'aria-expanded', ! p.hasClass( 'closed' ) );
+			});
 		},
 
 		save_state : function(page) {