diff --git a/.changeset/tame-ads-heal.md b/.changeset/tame-ads-heal.md
new file mode 100644
index 00000000..484f8a03
--- /dev/null
+++ b/.changeset/tame-ads-heal.md
@@ -0,0 +1,5 @@
+---
+"bits-ui": patch
+---
+
+Radio Group: allow both arrow up/down and left/right per WAI-ARIA spec
diff --git a/packages/bits-ui/src/lib/bits/radio-group/radio-group.svelte.ts b/packages/bits-ui/src/lib/bits/radio-group/radio-group.svelte.ts
index 44f46ec4..8af6d621 100644
--- a/packages/bits-ui/src/lib/bits/radio-group/radio-group.svelte.ts
+++ b/packages/bits-ui/src/lib/bits/radio-group/radio-group.svelte.ts
@@ -119,7 +119,7 @@ class RadioGroupItemState {
 	};
 
 	#onkeydown = (e: KeyboardEvent) => {
-		this.#root.rovingFocusGroup.handleKeydown(this.#ref.current, e);
+		this.#root.rovingFocusGroup.handleKeydown(this.#ref.current, e, true);
 	};
 
 	#tabIndex = $derived.by(() => this.#root.rovingFocusGroup.getTabIndex(this.#ref.current));
diff --git a/packages/bits-ui/src/lib/internal/use-roving-focus.svelte.ts b/packages/bits-ui/src/lib/internal/use-roving-focus.svelte.ts
index 31e73586..4093c3b9 100644
--- a/packages/bits-ui/src/lib/internal/use-roving-focus.svelte.ts
+++ b/packages/bits-ui/src/lib/internal/use-roving-focus.svelte.ts
@@ -74,7 +74,11 @@ export function useRovingFocus(props: UseRovingFocusProps) {
 		items[0]?.focus();
 	}
 
-	function handleKeydown(node: HTMLElement | null | undefined, e: KeyboardEvent) {
+	function handleKeydown(
+		node: HTMLElement | null | undefined,
+		e: KeyboardEvent,
+		both: boolean = false
+	) {
 		const rootNode = document.getElementById(props.rootNodeId.current);
 		if (!rootNode || !node) return;
 
@@ -94,6 +98,13 @@ export function useRovingFocus(props: UseRovingFocusProps) {
 			[kbd.END]: items.length - 1,
 		};
 
+		if (both) {
+			const altNextKey = nextKey === kbd.ARROW_DOWN ? kbd.ARROW_RIGHT : kbd.ARROW_DOWN;
+			const altPrevKey = prevKey === kbd.ARROW_UP ? kbd.ARROW_LEFT : kbd.ARROW_UP;
+			keyToIndex[altNextKey] = currentIndex + 1;
+			keyToIndex[altPrevKey] = currentIndex - 1;
+		}
+
 		let itemIndex = keyToIndex[e.key];
 		if (itemIndex === undefined) return;
 		e.preventDefault();