diff --git a/src/api/attributes.spec.ts b/src/api/attributes.spec.ts
index 5b97d8ab63..959ad3a6e2 100644
--- a/src/api/attributes.spec.ts
+++ b/src/api/attributes.spec.ts
@@ -797,6 +797,22 @@ describe('$(...)', () => {
 
       expect($text('body').html()).toBe(mixedText);
     });
+
+    it('(KEY) : should be case-insensitive in HTML mode', () => {
+      const $html = load('<div class="test"></div>');
+      $html('div').removeAttr('CLASS');
+      expect($html('div').attr('class')).toBeUndefined();
+    });
+
+    it('(KEY) : should remain case-sensitive in XML mode', () => {
+      const $xml = load('<Foo Bar="x"></Foo>', { xmlMode: true });
+      // A differently-cased name must not remove the attribute in XML mode.
+      $xml('Foo').removeAttr('BAR');
+      expect($xml('Foo').attr('Bar')).toBe('x');
+      // The exact name still removes it.
+      $xml('Foo').removeAttr('Bar');
+      expect($xml('Foo').attr('Bar')).toBeUndefined();
+    });
   });
 
   describe('.hasClass', () => {
diff --git a/src/api/attributes.ts b/src/api/attributes.ts
index dbd46dad9e..5529527c8d 100644
--- a/src/api/attributes.ts
+++ b/src/api/attributes.ts
@@ -880,8 +880,10 @@ export function removeAttr<T extends AnyNode>(
   const attrNames = splitNames(name);
 
   for (const attrName of attrNames) {
+    // HTML attribute names are case-insensitive; XML mode preserves case.
+    const lookup = this.options.xmlMode ? attrName : attrName.toLowerCase();
     domEach(this, (elem) => {
-      if (isTag(elem)) removeAttribute(elem, attrName);
+      if (isTag(elem)) removeAttribute(elem, lookup);
     });
   }