diff --git a/packages/components/CHANGELOG.md b/packages/components/CHANGELOG.md
index 9c58e2f84faddb..5011f643491944 100644
--- a/packages/components/CHANGELOG.md
+++ b/packages/components/CHANGELOG.md
@@ -18,6 +18,7 @@
 
 -    The `Button` component now displays the label as the tooltip for icon only buttons. ([#40716](https://github.com/WordPress/gutenberg/pull/40716))
 -    Use fake timers and fix usage of async methods from `@testing-library/user-event`. ([#40790](https://github.com/WordPress/gutenberg/pull/40790))
+-    UnitControl: avoid calling onChange callback twice when unit changes. ([#40796](https://github.com/WordPress/gutenberg/pull/40796))
 
 ### Internal
 
diff --git a/packages/components/src/unit-control/index.tsx b/packages/components/src/unit-control/index.tsx
index e97bc6ff955f6a..3296438b04b8c4 100644
--- a/packages/components/src/unit-control/index.tsx
+++ b/packages/components/src/unit-control/index.tsx
@@ -178,10 +178,7 @@ function UnforwardedUnitControl(
 				: undefined;
 			const changeProps = { event, data };
 
-			onChangeProp?.(
-				`${ validParsedQuantity ?? '' }${ validParsedUnit }`,
-				changeProps
-			);
+			// The `onChange` callback already gets called, no need to call it explicitely.
 			onUnitChange?.( validParsedUnit, changeProps );
 
 			setUnit( validParsedUnit );
diff --git a/packages/components/src/unit-control/test/index.tsx b/packages/components/src/unit-control/test/index.tsx
index 7677622f277c3c..c57af0e75a7379 100644
--- a/packages/components/src/unit-control/test/index.tsx
+++ b/packages/components/src/unit-control/test/index.tsx
@@ -310,8 +310,7 @@ describe( 'UnitControl', () => {
 			// Clicking document.body to trigger a blur event on the input.
 			await user.click( document.body );
 
-			// TODO: investigate why `onChange` gets called twice instead of once
-			expect( onChangeSpy ).toHaveBeenCalledTimes( 2 );
+			expect( onChangeSpy ).toHaveBeenCalledTimes( 1 );
 			expect( onChangeSpy ).toHaveBeenLastCalledWith( '41vh' );
 
 			expect( onUnitChangeSpy ).toHaveBeenCalledTimes( 1 );