diff --git a/sdk/core/azure-core/CHANGELOG.md b/sdk/core/azure-core/CHANGELOG.md
index c45caf490aa6..6ee9aee17722 100644
--- a/sdk/core/azure-core/CHANGELOG.md
+++ b/sdk/core/azure-core/CHANGELOG.md
@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- Fixed PipelineClient.format_url to avoid adding trailing slashes when the URL template contains only query parameters.
+
 ### Other Changes
 
 ## 1.38.0 (2026-01-12)
diff --git a/sdk/core/azure-core/azure/core/pipeline/transport/_base.py b/sdk/core/azure-core/azure/core/pipeline/transport/_base.py
index a853bafda8e4..ec7d5bc5fa85 100644
--- a/sdk/core/azure-core/azure/core/pipeline/transport/_base.py
+++ b/sdk/core/azure-core/azure/core/pipeline/transport/_base.py
@@ -130,9 +130,10 @@ def _urljoin(base_url: str, stub_url: str) -> str:
 
     # Note that _replace is a public API named that way to avoid conflicts in namedtuple
     # https://docs.python.org/3/library/collections.html?highlight=namedtuple#collections.namedtuple
-    parsed_base_url = parsed_base_url._replace(
-        path=parsed_base_url.path.rstrip("/") + "/" + stub_url_path,
-    )
+    if stub_url_path:
+        parsed_base_url = parsed_base_url._replace(
+            path=parsed_base_url.path.rstrip("/") + "/" + stub_url_path,
+        )
     if stub_url_query:
         query_params = [stub_url_query]
         if parsed_base_url.query:
diff --git a/sdk/core/azure-core/tests/test_basic_transport.py b/sdk/core/azure-core/tests/test_basic_transport.py
index 24d3790f0590..2f8cfd70c8c1 100644
--- a/sdk/core/azure-core/tests/test_basic_transport.py
+++ b/sdk/core/azure-core/tests/test_basic_transport.py
@@ -128,7 +128,8 @@ def test_http_request_serialization(http_request):
 
 @pytest.mark.parametrize("http_request", HTTP_REQUESTS)
 def test_url_join(http_request):
-    assert _urljoin("devstoreaccount1", "") == "devstoreaccount1/"
+    assert _urljoin("devstoreaccount1", "?testdir") == "devstoreaccount1?testdir"
+    assert _urljoin("devstoreaccount1", "") == "devstoreaccount1"
     assert _urljoin("devstoreaccount1", "testdir/") == "devstoreaccount1/testdir/"
     assert _urljoin("devstoreaccount1/", "") == "devstoreaccount1/"
     assert _urljoin("devstoreaccount1/", "testdir/") == "devstoreaccount1/testdir/"