diff --git a/packages/material-ui-lab/src/TreeItem/TreeItem.js b/packages/material-ui-lab/src/TreeItem/TreeItem.js
index edbdc1b67bc96a..461f51551362da 100644
--- a/packages/material-ui-lab/src/TreeItem/TreeItem.js
+++ b/packages/material-ui-lab/src/TreeItem/TreeItem.js
@@ -366,13 +366,13 @@ const TreeItem = React.forwardRef(function TreeItem(props, ref) {
   }, [focused]);
 
   let ariaSelected;
-  if (!selectionDisabled) {
-    if (multiSelect) {
-      ariaSelected = selected;
-    } else if (selected) {
-      ariaSelected = true;
-    }
+  if (multiSelect) {
+    ariaSelected = selected;
+  } else if (selected) {
+    // single-selection trees unset aria-selected
+    ariaSelected = true;
   }
+
   return (
     <li
       className={clsx(classes.root, className, {
diff --git a/packages/material-ui-lab/src/TreeItem/TreeItem.test.js b/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
index 21e6d7eea86383..f7c4232dcc198b 100644
--- a/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
+++ b/packages/material-ui-lab/src/TreeItem/TreeItem.test.js
@@ -251,14 +251,14 @@ describe('<TreeItem />', () => {
           expect(getByTestId('test')).to.have.attribute('aria-selected', 'true');
         });
 
-        it('should not have the attribute `aria-selected` if disableSelection is true', () => {
+        it('should have the attribute `aria-selected` if disableSelection is true', () => {
           const { getByTestId } = render(
             <TreeView multiSelect disableSelection>
               <TreeItem nodeId="test" label="test" data-testid="test" />
             </TreeView>,
           );
 
-          expect(getByTestId('test')).to.not.have.attribute('aria-selected');
+          expect(getByTestId('test')).to.have.attribute('aria-selected', 'false');
         });
       });
     });