diff --git a/google/cloud/_http.py b/google/cloud/_http.py
index b6aedce..74539a5 100644
--- a/google/cloud/_http.py
+++ b/google/cloud/_http.py
@@ -14,11 +14,13 @@
 
 """Shared implementation of connections to API servers."""
 
+import collections
 import json
 import platform
 import warnings
 
 from pkg_resources import get_distribution
+from six.moves import collections_abc
 from six.moves.urllib.parse import urlencode
 
 from google.api_core.client_info import ClientInfo
@@ -212,9 +214,15 @@ def build_api_url(
 
         query_params = query_params or {}
 
-        if "prettyPrint" not in query_params:
+        if isinstance(query_params, collections_abc.Mapping):
             query_params = query_params.copy()
-            query_params["prettyPrint"] = "false"
+        else:
+            query_params_dict = collections.defaultdict(list)
+            for key, value in query_params:
+                query_params_dict[key].append(value)
+            query_params = query_params_dict
+
+        query_params.setdefault("prettyPrint", "false")
 
         url += "?" + urlencode(query_params, doseq=True)
 
diff --git a/tests/unit/test__http.py b/tests/unit/test__http.py
index bd50b1e..069ddc0 100644
--- a/tests/unit/test__http.py
+++ b/tests/unit/test__http.py
@@ -210,6 +210,25 @@ def test_build_api_url_w_extra_query_params(self):
         parms = dict(parse_qs(qs))
         self.assertEqual(parms["bar"], ["baz"])
         self.assertEqual(parms["qux"], ["quux", "corge"])
+        self.assertEqual(parms["prettyPrint"], ["false"])
+
+    def test_build_api_url_w_extra_query_params_tuples(self):
+        from six.moves.urllib.parse import parse_qs
+        from six.moves.urllib.parse import urlsplit
+
+        client = object()
+        conn = self._make_mock_one(client)
+        uri = conn.build_api_url("/foo", [("bar", "baz"), ("qux", "quux"), ("qux", "corge")])
+
+        scheme, netloc, path, qs, _ = urlsplit(uri)
+        self.assertEqual("%s://%s" % (scheme, netloc), conn.API_BASE_URL)
+        # Intended to emulate mock_template
+        PATH = "/".join(["", "mock", conn.API_VERSION, "foo"])
+        self.assertEqual(path, PATH)
+        parms = dict(parse_qs(qs))
+        self.assertEqual(parms["bar"], ["baz"])
+        self.assertEqual(parms["qux"], ["quux", "corge"])
+        self.assertEqual(parms["prettyPrint"], ["false"])
 
     def test__make_request_no_data_no_content_type_no_headers(self):
         from google.cloud._http import CLIENT_INFO_HEADER