diff --git a/blocks/navigation/renderer.php b/blocks/navigation/renderer.php
index 3c99b3bc4a4..d39012cd4e2 100644
--- a/blocks/navigation/renderer.php
+++ b/blocks/navigation/renderer.php
@@ -74,18 +74,20 @@ class block_navigation_renderer extends plugin_renderer_base {
 
             // this applies to the li item which contains all child lists too
             $liclasses = array($item->get_css_type(), 'depth_'.$depth);
+            $liexpandable = array();
             if ($item->has_children() && (!$item->forceopen || $item->collapse)) {
                 $liclasses[] = 'collapsed';
             }
             if ($isbranch) {
                 $liclasses[] = 'contains_branch';
+                $liexpandable = array('aria-expanded' => in_array('collapsed', $liclasses) ? "false" : "true");
             } else if ($hasicon) {
                 $liclasses[] = 'item_with_icon';
             }
             if ($item->isactive === true) {
                 $liclasses[] = 'current_branch';
             }
-            $liattr = array('class'=>join(' ',$liclasses));
+            $liattr = array('class' => join(' ',$liclasses)) + $liexpandable;
             // class attribute on the div item which only contains the item content
             $divclasses = array('tree_item');
             if ($isbranch) {
diff --git a/blocks/navigation/yui/navigation/navigation.js b/blocks/navigation/yui/navigation/navigation.js
index 180977d90ba..2189d51eed2 100644
--- a/blocks/navigation/yui/navigation/navigation.js
+++ b/blocks/navigation/yui/navigation/navigation.js
@@ -162,16 +162,20 @@ TREE.prototype = {
                 switch (e.action) {
                     case 'expand' :
                         target.removeClass('collapsed');
+                        target.set('aria-expanded', true);
                         break;
                     case 'collapse' :
                         target.addClass('collapsed');
+                        target.set('aria-expanded', false);
                         break;
                     default :
                         target.toggleClass('collapsed');
+                        target.set('aria-expanded', !target.hasClass('collapsed'));
                 }
                 e.halt();
             } else {
                 target.toggleClass('collapsed');
+                target.set('aria-expanded', !target.hasClass('collapsed'));
             }
         }
 
@@ -180,6 +184,7 @@ TREE.prototype = {
             target.siblings('li').each(function(){
                 if (this.get('id') !== target.get('id') && !this.hasClass('collapsed')) {
                     this.addClass('collapsed');
+                    this.set('aria-expanded', false);
                 }
             });
         }
@@ -287,6 +292,7 @@ BRANCH.prototype = {
         }
         if (isbranch) {
             branchli.addClass('collapsed').addClass('contains_branch');
+            branchli.set('aria-expanded', false);
             branchp.addClass('branch');
         }
 
diff --git a/blocks/settings/renderer.php b/blocks/settings/renderer.php
index 41cea8742c2..a19d41e03f9 100644
--- a/blocks/settings/renderer.php
+++ b/blocks/settings/renderer.php
@@ -40,18 +40,20 @@ class block_settings_renderer extends plugin_renderer_base {
 
             // this applies to the li item which contains all child lists too
             $liclasses = array($item->get_css_type());
+            $liexpandable = array();
             if (!$item->forceopen || (!$item->forceopen && $item->collapse) || ($item->children->count()==0  && $item->nodetype==navigation_node::NODETYPE_BRANCH)) {
                 $liclasses[] = 'collapsed';
             }
             if ($isbranch) {
                 $liclasses[] = 'contains_branch';
+                $liexpandable = array('aria-expanded' => in_array('collapsed', $liclasses) ? "false" : "true");
             } else if ($hasicon) {
                 $liclasses[] = 'item_with_icon';
             }
             if ($item->isactive === true) {
                 $liclasses[] = 'current_branch';
             }
-            $liattr = array('class'=>join(' ',$liclasses));
+            $liattr = array('class' => join(' ',$liclasses)) + $liexpandable;
             // class attribute on the div item which only contains the item content
             $divclasses = array('tree_item');
             if ($isbranch) {