diff --git a/plugins/inputs/mongodb/README.md b/plugins/inputs/mongodb/README.md
index c98736335..545511c92 100644
--- a/plugins/inputs/mongodb/README.md
+++ b/plugins/inputs/mongodb/README.md
@@ -12,6 +12,10 @@ All MongoDB server versions from 2.6 and higher are supported.
   ## For example:
   ##   mongodb://user:auth_key@10.10.3.30:27017,
   ##   mongodb://10.10.3.33:18832,
+  ##
+  ## If connecting to a cluster, users must include the "?connect=direct" in
+  ## the URL to ensure that the connection goes directly to the specified node
+  ## and not have all connections passed to the master node.
   servers = ["mongodb://127.0.0.1:27017/?connect=direct"]
 
   ## When true, collect cluster status.
diff --git a/plugins/inputs/mongodb/sample.conf b/plugins/inputs/mongodb/sample.conf
index 9b3b0f27d..5e9fbba17 100644
--- a/plugins/inputs/mongodb/sample.conf
+++ b/plugins/inputs/mongodb/sample.conf
@@ -5,6 +5,10 @@
   ## For example:
   ##   mongodb://user:auth_key@10.10.3.30:27017,
   ##   mongodb://10.10.3.33:18832,
+  ##
+  ## If connecting to a cluster, users must include the "?connect=direct" in
+  ## the URL to ensure that the connection goes directly to the specified node
+  ## and not have all connections passed to the master node.
   servers = ["mongodb://127.0.0.1:27017/?connect=direct"]
 
   ## When true, collect cluster status.