diff --git a/packages/fluentui/CHANGELOG.md b/packages/fluentui/CHANGELOG.md
index cc90a074beae8..3886f12f1f2db 100644
--- a/packages/fluentui/CHANGELOG.md
+++ b/packages/fluentui/CHANGELOG.md
@@ -20,6 +20,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Fixes
 - `Popup` should not dismiss when its iframe content is focused @ling1726 ([#19955](https://github.com/microsoft/fluentui/pull/19955))
+- `whatInput` Add typings to what input event listeners @ling1726 ([#20024](https://github.com/microsoft/fluentui/pull/20024))
 
 
 <!--------------------------------[ v0.59.0 ]------------------------------- -->
diff --git a/packages/fluentui/react-northstar/src/utils/whatInput.ts b/packages/fluentui/react-northstar/src/utils/whatInput.ts
index 33e0cab974a18..452ecadfabd35 100644
--- a/packages/fluentui/react-northstar/src/utils/whatInput.ts
+++ b/packages/fluentui/react-northstar/src/utils/whatInput.ts
@@ -73,6 +73,8 @@ const setUp = () => {
   doUpdate(window.document);
 };
 
+type WhatInputEvents = MouseEvent | TouchEvent | KeyboardEvent;
+
 /*
  * events
  */
@@ -107,7 +109,7 @@ const addListeners = (eventTarget: Window) => {
 };
 
 // checks conditions before updating new input
-const setInput = event => {
+const setInput = (event: WhatInputEvents) => {
   // only execute if the event buffer timer isn't running
   if (!isBuffering) {
     const eventKey = event.which;
@@ -133,7 +135,7 @@ const doUpdate = (target: Document) => {
 };
 
 // buffers events that frequently also fire mouse events
-const eventBuffer = event => {
+const eventBuffer = (event: WhatInputEvents) => {
   // set the current input
   setInput(event);