diff --git a/firestore/docs/index.rst b/firestore/docs/index.rst
index d355d8aec4c8..b8157df9bd0c 100644
--- a/firestore/docs/index.rst
+++ b/firestore/docs/index.rst
@@ -1,5 +1,12 @@
 .. include:: README.rst
 
+.. note::
+
+   Because the firestore client uses :mod:`grpcio` library, it is safe to
+   share instances across threads. In multiprocessing scenarios, the best
+   practice is to create client instances *after* the invocation of
+   :func:`os.fork` by :class:`multiprocessing.Pool` or
+   :class:`multiprocessing.Process`.
 
 API Reference
 -------------