diff --git a/includes/Checker/Checks/Plugin_Repo/Premium_Only_Function_Check.php b/includes/Checker/Checks/Plugin_Repo/Premium_Only_Function_Check.php
new file mode 100644
index 000000000..08bdf319d
--- /dev/null
+++ b/includes/Checker/Checks/Plugin_Repo/Premium_Only_Function_Check.php
@@ -0,0 +1,91 @@
+<?php
+/**
+ * Class Premium_Only_Function_Check.
+ *
+ * @package plugin-check
+ */
+
+namespace WordPress\Plugin_Check\Checker\Checks\Plugin_Repo;
+
+use WordPress\Plugin_Check\Checker\Check_Categories;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\Abstract_File_Check;
+use WordPress\Plugin_Check\Traits\Amend_Check_Result;
+use WordPress\Plugin_Check\Traits\Stable_Check;
+
+/**
+ * Check to detect functions ending in __premium_only.
+ *
+ * @since x.x.x
+ */
+class Premium_Only_Function_Check extends Abstract_File_Check {
+
+	use Amend_Check_Result;
+	use Stable_Check;
+
+	/**
+	 * Gets the categories for the check.
+	 *
+	 * Every check must have at least one category.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return array The categories for the check.
+	 */
+	public function get_categories() {
+		return array( Check_Categories::CATEGORY_PLUGIN_REPO );
+	}
+
+	/**
+	 * Amends the given result by running the check on the given list of files.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param Check_Result $result The check result to amend.
+	 * @param array        $files  List of absolute file paths.
+	 */
+	protected function check_files( Check_Result $result, array $files ) {
+		$php_files = self::filter_files_by_extension( $files, 'php' );
+		$matches   = self::files_preg_match_all( '/\bfunction\s+[a-zA-Z_\x80-\xff][a-zA-Z0-9_\x80-\xff]*__premium_only\s*\(/i', $php_files );
+
+		if ( ! empty( $matches ) ) {
+			foreach ( $matches as $match ) {
+				$this->add_result_error_for_file(
+					$result,
+					__( 'Function declarations ending in __premium_only look like premium/pro-only code and should not be included in a WordPress.org plugin.', 'plugin-check' ),
+					'premium_only_function_found',
+					$match['file'],
+					$match['line'],
+					$match['column'],
+					'https://developer.wordpress.org/plugins/wordpress-org/detailed-plugin-guidelines/'
+				);
+			}
+		}
+	}
+
+	/**
+	 * Gets the description for the check.
+	 *
+	 * Every check must have a short description explaining what the check does.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return string Description.
+	 */
+	public function get_description(): string {
+		return __( 'Detects function declarations ending in __premium_only.', 'plugin-check' );
+	}
+
+	/**
+	 * Gets the documentation URL for the check.
+	 *
+	 * Every check must have a URL with further information about the check.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return string The documentation URL.
+	 */
+	public function get_documentation_url(): string {
+		return __( 'https://developer.wordpress.org/plugins/wordpress-org/detailed-plugin-guidelines/', 'plugin-check' );
+	}
+}
diff --git a/includes/Checker/Default_Check_Repository.php b/includes/Checker/Default_Check_Repository.php
index d4d5c548d..3c335614e 100644
--- a/includes/Checker/Default_Check_Repository.php
+++ b/includes/Checker/Default_Check_Repository.php
@@ -14,6 +14,7 @@
  */
 class Default_Check_Repository extends Empty_Check_Repository {
 
+
 	/**
 	 * True if the class was fully initialized.
 	 *
@@ -105,6 +106,7 @@ private function register_default_checks() {
 				'external_admin_menu_links'  => new Checks\Plugin_Repo\External_Admin_Menu_Links_Check(),
 				'wp_functions_compatibility' => new Checks\Plugin_Repo\WP_Functions_Compatibility_Check(),
 				'ai_provider'                => new Checks\General\AI_Provider_Check(),
+				'premium_only_function'      => new Checks\Plugin_Repo\Premium_Only_Function_Check(),
 			)
 		);
 
diff --git a/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-with-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-with-errors/load.php
new file mode 100644
index 000000000..ff1d13a2f
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-with-errors/load.php
@@ -0,0 +1,18 @@
+<?php
+/**
+ * Plugin Name: Premium Only Function Test
+ * Description: Test plugin containing functions named with the __premium_only suffix.
+ * Version: 1.0.0
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+function poft_register_settings__premium_only() {
+	register_setting( 'poft_settings', 'poft_enabled' );
+}
+
+function poft_admin_notice__premium_only() {
+	echo '<div class="notice notice-info"><p>Premium-only test notice.</p></div>';
+}
diff --git a/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-without-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-without-errors/load.php
new file mode 100644
index 000000000..58209ef5a
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-premium-only-function-without-errors/load.php
@@ -0,0 +1,18 @@
+<?php
+/**
+ * Plugin Name: Premium Only Function Clean Test
+ * Description: Test plugin containing standard functions without __premium_only suffix.
+ * Version: 1.0.0
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+function poft_register_settings() {
+	register_setting( 'poft_settings', 'poft_enabled' );
+}
+
+function poft_admin_notice() {
+	echo '<div class="notice notice-info"><p>Standard test notice.</p></div>';
+}
diff --git a/tests/phpunit/tests/Checker/Checks/Premium_Only_Function_Check_Tests.php b/tests/phpunit/tests/Checker/Checks/Premium_Only_Function_Check_Tests.php
new file mode 100644
index 000000000..b4abe9aef
--- /dev/null
+++ b/tests/phpunit/tests/Checker/Checks/Premium_Only_Function_Check_Tests.php
@@ -0,0 +1,45 @@
+<?php
+/**
+ * Tests for the Premium_Only_Function_Check class.
+ *
+ * @package plugin-check
+ */
+
+use WordPress\Plugin_Check\Checker\Check_Context;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\Plugin_Repo\Premium_Only_Function_Check;
+
+class Premium_Only_Function_Check_Tests extends WP_UnitTestCase {
+
+	public function test_run_with_errors() {
+		$check         = new Premium_Only_Function_Check();
+		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-premium-only-function-with-errors/load.php' );
+		$check_result  = new Check_Result( $check_context );
+
+		$check->run( $check_result );
+
+		$errors = $check_result->get_errors();
+
+		$this->assertNotEmpty( $errors );
+		$this->assertArrayHasKey( 'load.php', $errors );
+		$this->assertSame( 2, $check_result->get_error_count() );
+
+		$this->assertArrayHasKey( 12, $errors['load.php'] );
+		$this->assertArrayHasKey( 16, $errors['load.php'] );
+		$this->assertSame( 'premium_only_function_found', $errors['load.php'][12][1][0]['code'] );
+		$this->assertSame( 'premium_only_function_found', $errors['load.php'][16][1][0]['code'] );
+	}
+
+	public function test_run_without_errors() {
+		$check         = new Premium_Only_Function_Check();
+		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-premium-only-function-without-errors/load.php' );
+		$check_result  = new Check_Result( $check_context );
+
+		$check->run( $check_result );
+
+		$errors = $check_result->get_errors();
+
+		$this->assertEmpty( $errors );
+		$this->assertSame( 0, $check_result->get_error_count() );
+	}
+}