diff --git a/pybigquery/_helpers.py b/pybigquery/_helpers.py
index 35f7e4ab..fc48144c 100644
--- a/pybigquery/_helpers.py
+++ b/pybigquery/_helpers.py
@@ -38,13 +38,13 @@ def create_bigquery_client(
             credentials_path
         )
         credentials = credentials.with_scopes(SCOPES)
-        default_project = credentials.project
+        default_project = credentials.project_id
     elif credentials_info:
         credentials = service_account.Credentials.from_service_account_info(
             credentials_info
         )
         credentials = credentials.with_scopes(SCOPES)
-        default_project = credentials.project
+        default_project = credentials.project_id
     else:
         credentials, default_project = google.auth.default(scopes=SCOPES)
 
diff --git a/tests/system/test_helpers.py b/tests/system/test_helpers.py
new file mode 100644
index 00000000..18334631
--- /dev/null
+++ b/tests/system/test_helpers.py
@@ -0,0 +1,74 @@
+# Copyright 2021 The PyBigQuery Authors
+#
+# Use of this source code is governed by an MIT-style
+# license that can be found in the LICENSE file or at
+# https://opensource.org/licenses/MIT.
+
+import os
+import json
+
+import pytest
+
+
+@pytest.fixture(scope="session")
+def module_under_test():
+    from pybigquery import _helpers
+
+    return _helpers
+
+
+@pytest.fixture
+def credentials_path():
+    if "GOOGLE_APPLICATION_CREDENTIALS" not in os.environ:
+        pytest.skip("GOOGLE_APPLICATION_CREDENTIALS must be set")
+    return os.environ["GOOGLE_APPLICATION_CREDENTIALS"]
+
+
+@pytest.fixture
+def credentials_info(credentials_path):
+    with open(credentials_path) as credentials_file:
+        return json.load(credentials_file)
+
+
+def test_create_bigquery_client_with_credentials_path(
+    module_under_test, credentials_path, credentials_info
+):
+    bqclient = module_under_test.create_bigquery_client(
+        credentials_path=credentials_path
+    )
+    assert bqclient.project == credentials_info["project_id"]
+
+
+def test_create_bigquery_client_with_credentials_path_respects_project(
+    module_under_test, credentials_path
+):
+    """Test that project_id is used, even when there is a default project.
+
+    https://github.com/googleapis/python-bigquery-sqlalchemy/issues/48
+    """
+    bqclient = module_under_test.create_bigquery_client(
+        credentials_path=credentials_path, project_id="connection-url-project",
+    )
+    assert bqclient.project == "connection-url-project"
+
+
+def test_create_bigquery_client_with_credentials_info(
+    module_under_test, credentials_info
+):
+    bqclient = module_under_test.create_bigquery_client(
+        credentials_info=credentials_info
+    )
+    assert bqclient.project == credentials_info["project_id"]
+
+
+def test_create_bigquery_client_with_credentials_info_respects_project(
+    module_under_test, credentials_info
+):
+    """Test that project_id is used, even when there is a default project.
+
+    https://github.com/googleapis/python-bigquery-sqlalchemy/issues/48
+    """
+    bqclient = module_under_test.create_bigquery_client(
+        credentials_info=credentials_info, project_id="connection-url-project",
+    )
+    assert bqclient.project == "connection-url-project"
diff --git a/tests/unit/test_helpers.py b/tests/unit/test_helpers.py
index 38be0453..1a3acc85 100644
--- a/tests/unit/test_helpers.py
+++ b/tests/unit/test_helpers.py
@@ -17,7 +17,7 @@ class AnonymousCredentialsWithProject(google.auth.credentials.AnonymousCredentia
 
     def __init__(self, project):
         super().__init__()
-        self.project = project
+        self.project_id = project
 
     def with_scopes(self, scopes):
         return self