diff --git a/synthtool/gcp/templates/python_library/docs/conf.py.j2 b/synthtool/gcp/templates/python_library/docs/conf.py.j2
index 35c8cb13c..0bfeed4d8 100644
--- a/synthtool/gcp/templates/python_library/docs/conf.py.j2
+++ b/synthtool/gcp/templates/python_library/docs/conf.py.j2
@@ -352,6 +352,7 @@ intersphinx_mapping = {
         None,
     ),
     "grpc": ("https://grpc.io/grpc/python/", None),
+    "proto-plus": ("https://proto-plus-python.readthedocs.io/en/latest/", None),
     {% if intersphinx_dependencies %}
         {% for name, url in intersphinx_dependencies.items() %}
             "{{ name }}": ("{{ url }}", None),