diff --git a/doc/releases/migration-guide-4.0.rst b/doc/releases/migration-guide-4.0.rst
index e1d6b9d52aa..acae5d9b97e 100644
--- a/doc/releases/migration-guide-4.0.rst
+++ b/doc/releases/migration-guide-4.0.rst
@@ -45,6 +45,27 @@ Trusted Firmware-M
 LVGL
 ====
 
+zcbor
+=====
+
+* Updated the zcbor library to version 0.9.0.
+  Full release notes at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/RELEASE_NOTES.md
+  Migration guide at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/MIGRATION_GUIDE.md
+  Migration guide copied here:
+
+  * `zcbor_simple_*()` functions have been removed to avoid confusion about their use.
+    They are still in the C file because they are used by other functions.
+    Instead, use the specific functions for the currently supported simple values, i.e.
+    `zcbor_bool_*()`, `zcbor_nil_*()`, and `zcbor_undefined_*()`.
+    If a removed variant is strictly needed, add your own forward declaration in your code.
+
+  * Code generation naming:
+
+    * More C keywords are now capitalized to avoid naming collision.
+      You might have to capitalize some instances if your code was generated to have those names.
+
+    * A fix was made to the naming of bstr elements with a .size specifier, which might mean that these elements change name in your code when you regenerate.
+
 Device Drivers and Devicetree
 *****************************
 
diff --git a/doc/releases/release-notes-4.0.rst b/doc/releases/release-notes-4.0.rst
index 8ac2713e701..48dd0b0b70f 100644
--- a/doc/releases/release-notes-4.0.rst
+++ b/doc/releases/release-notes-4.0.rst
@@ -353,6 +353,20 @@ Trusted Firmware-M
 LVGL
 ****
 
+zcbor
+*****
+
+* Updated the zcbor library to version 0.9.0.
+  Full release notes at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/RELEASE_NOTES.md
+  Migration guide at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/MIGRATION_GUIDE.md
+  Highlights:
+
+    * Many code generation bugfixes
+
+    * You can now decide at run-time whether the decoder should enforce canonical encoding.
+
+    * Allow --file-header to accept a path to a file with header contents
+
 Tests and Samples
 *****************