diff --git a/README.md b/README.md
index c1fbe82..9f7468d 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,6 @@
-# PostCSS CSS-in-JS Syntax
+# PostCSS CSS-in-JS Syntax (deprecated)
+
+__This syntax is deprecated. Please refer to the [Stylelint v15 migration guide](https://github.com/stylelint/stylelint/blob/main/docs/migration-guide/to-15.md).__
 
 [![NPM version](https://img.shields.io/npm/v/@stylelint/postcss-css-in-js.svg)](https://www.npmjs.org/package/@stylelint/postcss-css-in-js) [![Build Status](https://github.com/stylelint/postcss-css-in-js/workflows/CI/badge.svg)](https://github.com/stylelint/postcss-css-in-js/actions)