diff --git a/source/upgrade.txt b/source/upgrade.txt
index 692ecdb5..e3b8247a 100644
--- a/source/upgrade.txt
+++ b/source/upgrade.txt
@@ -104,6 +104,14 @@ and upgrade versions.
 
 .. diagram for this example?
 
+.. _version-4.9-breaking-changes:
+
+Version 4.9 Breaking Changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- You must use ``pymongocrypt`` v1.10 or later to use :manual:`Client-Side Field 
+  Level Encryption </core/csfle>` (CSFLE) in your application.
+
 .. _version-4.8-breaking-changes:
 
 Version 4.8 Breaking Changes
diff --git a/source/whats-new.txt b/source/whats-new.txt
index cae1f0ec..2df9fd59 100644
--- a/source/whats-new.txt
+++ b/source/whats-new.txt
@@ -47,6 +47,11 @@ The {+driver-short+} v4.10 release includes the following new features:
 What's New in 4.9
 -----------------
 
+.. warning:: Breaking Changes
+
+   {+driver-short+} v4.9 contains breaking changes. For more information, see
+   :ref:`version-4.9-breaking-changes`.
+
 The {+driver-short+} v4.9 release includes the following new features:
 
 - Adds support for {+mdb-server+} 8.0 and Python 3.13.
@@ -56,6 +61,7 @@ The {+driver-short+} v4.9 release includes the following new features:
   Encryption </core/queryable-encryption>` in the {+mdb-server+} manual.
 - Adds a new experimental asynchronous API as a replacement for Motor. This API
   is in beta and is subject to change before the generally available release.
+
 .. TODO: Add link to the Pymongo Async migration guide
 
 .. _version-4.8: