diff --git a/administrator/templates/atum/error_full.php b/administrator/templates/atum/error_full.php
index 5d64cb5ea82da..ed6137df32078 100644
--- a/administrator/templates/atum/error_full.php
+++ b/administrator/templates/atum/error_full.php
@@ -206,10 +206,10 @@
             <div id="sidebar-wrapper" class="sidebar-wrapper sidebar-menu" <?php echo $hiddenMenu ? 'data-hidden="' . $hiddenMenu . '"' : ''; ?>>
                 <div id="sidebarmenu">
                     <div class="sidebar-toggle item item-level-1">
-                        <a id="menu-collapse" href="#" aria-label="<?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?>">
+                        <button id="menu-collapse" type="button" aria-expanded="true" aria-controls="sidebar-wrapper" aria-label="<?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?>">
                             <span id="menu-collapse-icon" class="icon-toggle-off icon-fw" aria-hidden="true"></span>
                             <span class="sidebar-item-title"><?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?></span>
-                        </a>
+                        </button>
                     </div>
                     <jdoc:include type="modules" name="menu" style="none" />
                 </div>
diff --git a/administrator/templates/atum/index.php b/administrator/templates/atum/index.php
index d3f96f135ae72..d32777c898172 100644
--- a/administrator/templates/atum/index.php
+++ b/administrator/templates/atum/index.php
@@ -188,10 +188,10 @@ function adjustColorLightness($r, $g, $b, $percent)
         <div id="sidebar-wrapper" class="sidebar-wrapper sidebar-menu" <?php echo $hiddenMenu ? 'data-hidden="' . $hiddenMenu . '"' : ''; ?>>
             <div id="sidebarmenu" class="sidebar-sticky">
                 <div class="sidebar-toggle item item-level-1">
-                    <a id="menu-collapse" href="#" aria-label="<?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?>">
+                    <button id="menu-collapse" type="button" aria-expanded="<?php echo $sidebarState === 'closed' ? 'false' : 'true'; ?>" aria-controls="sidebar-wrapper" aria-label="<?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?>">
                         <span id="menu-collapse-icon" class="<?php echo $sidebarState === 'closed' ? 'icon-toggle-on' : 'icon-toggle-off'; ?> icon-fw" aria-hidden="true"></span>
                         <span class="sidebar-item-title"><?php echo Text::_('JTOGGLE_SIDEBAR_MENU'); ?></span>
-                    </a>
+                    </button>
                 </div>
                 <jdoc:include type="modules" name="menu" style="none" />
             </div>
diff --git a/media_source/mod_menu/js/admin-menu.es6.js b/media_source/mod_menu/js/admin-menu.es6.js
index 4928104d1888a..2d7f8b0389004 100644
--- a/media_source/mod_menu/js/admin-menu.es6.js
+++ b/media_source/mod_menu/js/admin-menu.es6.js
@@ -5,6 +5,7 @@
 
 const wrapper = document.getElementById('wrapper');
 const sidebar = document.getElementById('sidebar-wrapper');
+const menuToggle = document.getElementById('menu-collapse');
 const menuToggleIcon = document.getElementById('menu-collapse-icon');
 
 // Strip server-side mm-show/mm-active, then re-apply after init (no visual flash).
@@ -51,7 +52,6 @@ if (!sidebar) {
 
 if (sidebar && !sidebar.getAttribute('data-hidden')) {
   // Sidebar
-  const menuToggle = document.getElementById('menu-collapse');
 
   // Apply 2nd level collapse
   sidebar.querySelectorAll('.collapse-level-1').forEach((first) => {
@@ -63,26 +63,37 @@ if (sidebar && !sidebar.getAttribute('data-hidden')) {
     });
   });
 
+  // Keep the button state in sync with the sidebar
+  const setMenuToggleState = (expanded) => {
+    menuToggle.setAttribute('aria-expanded', String(expanded));
+  };
+
+  setMenuToggleState(!wrapper.classList.contains('closed'));
+
   // Toggle menu
-  menuToggle.addEventListener('click', (event) => {
-    event.preventDefault();
-    wrapper.classList.toggle('closed');
-    menuToggleIcon.classList.toggle('icon-toggle-on');
-    menuToggleIcon.classList.toggle('icon-toggle-off');
+  if (menuToggle) {
+    menuToggle.addEventListener('click', () => {
+      wrapper.classList.toggle('closed');
+      menuToggleIcon.classList.toggle('icon-toggle-on');
+      menuToggleIcon.classList.toggle('icon-toggle-off');
 
-    document.querySelectorAll('.main-nav > li').forEach((item) => item.classList.remove('open'));
+      const expanded = !wrapper.classList.contains('closed');
+      setMenuToggleState(expanded);
 
-    const elem = document.querySelector('.child-open');
-    if (elem) {
-      elem.classList.remove('child-open');
-    }
+      document.querySelectorAll('.main-nav > li').forEach((item) => item.classList.remove('open'));
 
-    window.dispatchEvent(new CustomEvent('joomla:menu-toggle', {
-      detail: wrapper.classList.contains('closed') ? 'closed' : 'open',
-      bubbles: true,
-      cancelable: true,
-    }));
-  });
+      const elem = document.querySelector('.child-open');
+      if (elem) {
+        elem.classList.remove('child-open');
+      }
+
+      window.dispatchEvent(new CustomEvent('joomla:menu-toggle', {
+        detail: expanded ? 'open' : 'closed',
+        bubbles: true,
+        cancelable: true,
+      }));
+    });
+  }
 
   // Sidebar Nav
   const mainNav = document.querySelector('ul.main-nav');
@@ -137,6 +148,7 @@ if (sidebar && !sidebar.getAttribute('data-hidden')) {
         menuToggleIcon.classList.toggle('icon-toggle-off');
         menuToggleIcon.classList.toggle('icon-toggle-on');
       }
+      setMenuToggleState(true);
       mainNav.classList.add('child-open');
 
       if (menuItem.parentNode.classList.contains('main-nav')) {
diff --git a/media_source/templates/administrator/atum/scss/blocks/_sidebar.scss b/media_source/templates/administrator/atum/scss/blocks/_sidebar.scss
index 071caf6b62584..577726f55acaa 100644
--- a/media_source/templates/administrator/atum/scss/blocks/_sidebar.scss
+++ b/media_source/templates/administrator/atum/scss/blocks/_sidebar.scss
@@ -19,6 +19,7 @@
     list-style-type: none;
 
     a,
+    button,
     .menu-dashboard,
     .menu-quicktask {
       color: $sidebar-item-color; /* $sidebar-item-color $white */
@@ -31,7 +32,8 @@
       }
     }
 
-    > a {
+    > a,
+    > button {
       position: relative;
       display: flex;
       flex-grow: 1;
@@ -70,8 +72,23 @@
   .sidebar-toggle {
     background: $sidebar-toggle-bg; /* $sidebar-toggle-bg var(--template-bg-dark-60) */
 
-    a {
+    button {
+      display: flex;
+      flex-grow: 1;
+      align-items: center;
+      min-block-size: 40px;
+      padding: 0;
       color: $sidebar-toggle-link; /* $sidebar-toggle-link $white */
+      text-align: start;
+      background: transparent;
+      border: 0;
+
+      &:focus-visible,
+      &.focus-visible {
+        border-radius: $border-radius;
+        outline: auto 2px $white;
+        outline-offset: -1px;
+      }
     }
 
     .sidebar-item-title {
diff --git a/tests/System/integration/plugins/system/shortcut/ShortcutPlugin.cy.js b/tests/System/integration/plugins/system/shortcut/ShortcutPlugin.cy.js
index a4b0434f9fc2b..1551744c2fbdf 100644
--- a/tests/System/integration/plugins/system/shortcut/ShortcutPlugin.cy.js
+++ b/tests/System/integration/plugins/system/shortcut/ShortcutPlugin.cy.js
@@ -65,16 +65,21 @@ describe('Test that the shortcut system plugin', () => {
 
   it('can toggle menu', () => {
     cy.visit('/administrator/index.php');
-    cy.get('#menu-collapse').contains('Toggle Menu').should('be.visible');
+    cy.get('#menu-collapse')
+      .should('be.visible')
+      .and('have.attr', 'type', 'button')
+      .and('have.attr', 'aria-expanded', 'true');
     cy.get('#wrapper').should('not.have.class', 'closed');
     cy.get('body').type('JM');
 
-    cy.get('#menu-collapse').contains('Toggle Menu').should('not.be.visible');
     cy.get('#wrapper').should('have.class', 'closed');
+    cy.get('#menu-collapse').should('have.attr', 'aria-expanded', 'false');
     cy.get('body').type('JM');
 
-    cy.get('#menu-collapse').contains('Toggle Menu').should('be.visible');
     cy.get('#wrapper').should('not.have.class', 'closed');
+    cy.get('#menu-collapse')
+      .should('be.visible')
+      .and('have.attr', 'aria-expanded', 'true');
   });
 
   it('can open dashboard', () => {