diff --git a/change/@fluentui-react-experiments-2d78d84b-e392-4d77-9619-42110f62351d.json b/change/@fluentui-react-experiments-2d78d84b-e392-4d77-9619-42110f62351d.json
new file mode 100644
index 0000000000000..eb950afeb9672
--- /dev/null
+++ b/change/@fluentui-react-experiments-2d78d84b-e392-4d77-9619-42110f62351d.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "unifiedpicker: make backspace delete work for pop out windows",
+  "packageName": "@fluentui/react-experiments",
+  "email": "litong@microsoft.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react-experiments/src/components/UnifiedPicker/UnifiedPicker.tsx b/packages/react-experiments/src/components/UnifiedPicker/UnifiedPicker.tsx
index ba5fc600bbb73..2d566951eacb2 100644
--- a/packages/react-experiments/src/components/UnifiedPicker/UnifiedPicker.tsx
+++ b/packages/react-experiments/src/components/UnifiedPicker/UnifiedPicker.tsx
@@ -371,7 +371,7 @@ export const UnifiedPicker = <T extends {}>(props: IUnifiedPickerProps<T>): JSX.
           input &&
           input.current &&
           !input.current.isValueSelected &&
-          input.current.inputElement === document.activeElement &&
+          input.current.inputElement === ev.currentTarget.ownerDocument.activeElement &&
           (input.current as Autofill).cursorLocation === 0
         ) {
           const indexToRemove = selectedItems.length - 1;