diff --git a/blocks/header/header.js b/blocks/header/header.js
index f7f719d5c2..6719d340e1 100644
--- a/blocks/header/header.js
+++ b/blocks/header/header.js
@@ -21,6 +21,21 @@ function closeOnEscape(e) {
   }
 }
 
+function closeOnFocusLost(e) {
+  const nav = e.currentTarget;
+  if (!nav.contains(e.relatedTarget)) {
+    const navSections = nav.querySelector('.nav-sections');
+    const navSectionExpanded = navSections.querySelector('[aria-expanded="true"]');
+    if (navSectionExpanded && isDesktop.matches) {
+      // eslint-disable-next-line no-use-before-define
+      toggleAllNavSections(navSections, false);
+    } else if (!isDesktop.matches) {
+      // eslint-disable-next-line no-use-before-define
+      toggleMenu(nav, navSections, false);
+    }
+  }
+}
+
 function openOnKeydown(e) {
   const focused = document.activeElement;
   const isNavDrop = focused.className === 'nav-drop';
@@ -77,12 +92,16 @@ function toggleMenu(nav, navSections, forceExpanded = null) {
       drop.removeEventListener('focus', focusNavSection);
     });
   }
+
   // enable menu collapse on escape keypress
   if (!expanded || isDesktop.matches) {
     // collapse menu on escape press
     window.addEventListener('keydown', closeOnEscape);
+    // collapse menu on focus lost
+    nav.addEventListener('focusout', closeOnFocusLost);
   } else {
     window.removeEventListener('keydown', closeOnEscape);
+    nav.removeEventListener('focusout', closeOnFocusLost);
   }
 }