diff --git a/guides/source/active_support_instrumentation.md b/guides/source/active_support_instrumentation.md
index 3b31557f41c29195e954d9b939ea5b38b2ac8c36..82168ffbdb028348789944723a48355538a15c1e 100644
--- a/guides/source/active_support_instrumentation.md
+++ b/guides/source/active_support_instrumentation.md
@@ -337,6 +337,22 @@ Action Mailer
 }
 ```
 
+### process.action_mailer
+
+| Key           | Value                    |
+| ------------- | ------------------------ |
+| `:mailer`     | Name of the mailer class |
+| `:action`     | The action               |
+| `:args`       | The arguments            |
+
+```ruby
+{
+  mailer: "Notification",
+  action: "welcome_email",
+  args: []
+}
+```
+
 Active Support
 --------------