diff --git a/packages/toolkit/src/query/tests/utils.test.ts b/packages/toolkit/src/query/tests/utils.test.ts
index 4b111b2a0..f99598a90 100644
--- a/packages/toolkit/src/query/tests/utils.test.ts
+++ b/packages/toolkit/src/query/tests/utils.test.ts
@@ -83,6 +83,12 @@ describe('joinUrls', () => {
 
     expect(joinUrls('', '/banana')).toBe('/banana')
     expect(joinUrls('', 'banana')).toBe('banana')
+
+    expect(joinUrls('/api', '?a=1')).toBe('/api?a=1')
+    expect(joinUrls('/api/', '?a=1')).toBe('/api/?a=1')
+
+    expect(joinUrls('/api', 'banana?a=1')).toBe('/api/banana?a=1')
+    expect(joinUrls('/api/', 'banana/?a=1')).toBe('/api/banana/?a=1')
   })
 
   test('correctly joins variations of absolute urls', () => {
diff --git a/packages/toolkit/src/query/utils/joinUrls.ts b/packages/toolkit/src/query/utils/joinUrls.ts
index f67533861..2087351df 100644
--- a/packages/toolkit/src/query/utils/joinUrls.ts
+++ b/packages/toolkit/src/query/utils/joinUrls.ts
@@ -18,8 +18,9 @@ export function joinUrls(
     return url
   }
 
+  const delimiter = base.endsWith('/') || !url.startsWith('?') ? '/' : ''
   base = withoutTrailingSlash(base)
   url = withoutLeadingSlash(url)
 
-  return `${base}/${url}`
+  return `${base}${delimiter}${url}`;
 }