diff --git a/theme/src/client/composables/layout.ts b/theme/src/client/composables/layout.ts
index f17e02b1..21133e7e 100644
--- a/theme/src/client/composables/layout.ts
+++ b/theme/src/client/composables/layout.ts
@@ -90,6 +90,7 @@ export function registerWatchers() {
     }, { passive: true })
   }
 
+  const { lang } = useData()
   const route = useRoute()
   const { disableSidebar, toggleSidebarCollapse } = useSidebarControl()
   watch(() => route.path, () => {
@@ -97,5 +98,11 @@ export function registerWatchers() {
     toggleSidebarCollapse(false)
   })
 
+  if (inBrowser) {
+    watch(lang, (newLang) => {
+      document.documentElement.lang = newLang
+    }, { immediate: true })
+  }
+
   useCloseSidebarOnEscape()
 }