diff --git a/includes/Checker/Checks/Plugin_Repo/Plugin_Readme_Check.php b/includes/Checker/Checks/Plugin_Repo/Plugin_Readme_Check.php
index 638f6f32b..d4cc2da9a 100644
--- a/includes/Checker/Checks/Plugin_Repo/Plugin_Readme_Check.php
+++ b/includes/Checker/Checks/Plugin_Repo/Plugin_Readme_Check.php
@@ -101,6 +101,9 @@ protected function check_files( Check_Result $result, array $files ) {
 
 		// Check the readme file for warnings.
 		$this->check_for_warnings( $result, $readme_file, $parser );
+
+		// Check the readme file for contributors.
+		$this->check_for_contributors( $result, $readme_file );
 	}
 
 	/**
@@ -652,6 +655,57 @@ private function check_for_warnings( Check_Result $result, string $readme_file,
 		}
 	}
 
+	/**
+	 * Checks the readme file for contributors.
+	 *
+	 * @since 1.2.0
+	 *
+	 * @param Check_Result $result      The Check Result to amend.
+	 * @param string       $readme_file Readme file.
+	 */
+	private function check_for_contributors( Check_Result $result, string $readme_file ) {
+		$regex = '/Contributors\s?:(.*?)\R/';
+
+		$matches = array();
+
+		self::file_preg_match( $regex, array( $readme_file ), $matches );
+
+		// Bail if no "Contributors" found.
+		if ( empty( $matches ) ) {
+			return;
+		}
+
+		$usernames = explode( ',', $matches[1] );
+
+		$usernames = array_map( 'trim', $usernames );
+
+		$valid = true;
+
+		foreach ( $usernames as $username ) {
+			if ( 1 !== preg_match( '/^[a-z0-9\s_.\-@]+$/', $username ) ) {
+				$valid = false;
+				break;
+			}
+		}
+
+		if ( ! $valid ) {
+			$this->add_result_warning_for_file(
+				$result,
+				sprintf(
+					/* translators: %s: plugin header field */
+					__( 'The "%s" header in the readme file must be a comma-separated list of WordPress.org-formatted usernames.', 'plugin-check' ),
+					'Contributors'
+				),
+				'readme_invalid_contributors',
+				$readme_file,
+				0,
+				0,
+				'',
+				6
+			);
+		}
+	}
+
 	/**
 	 * Returns current major WordPress version.
 	 *
diff --git a/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-md-with-errors/readme.md b/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-md-with-errors/readme.md
index 06c49edf3..a6e6ce7e9 100644
--- a/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-md-with-errors/readme.md
+++ b/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-md-with-errors/readme.md
@@ -1,7 +1,7 @@
 
 === Plugin Check ===
 
-Contributors:      wordpressdotorg
+Contributors:      https://johndoe.com
 Requires at least: 6.0
 Tested up to:      6.1
 Requires PHP:      5.6
@@ -10,4 +10,4 @@ License:           Oculus VR Inc. Software Development Kit License
 License URI:       https://www.gnu.org/licenses/gpl-2.0.html
 Tags:              performance, testing, security
 
-Here is a short description of the plugin.
\ No newline at end of file
+Here is a short description of the plugin.
diff --git a/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-parser-warnings/readme.txt b/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-parser-warnings/readme.txt
index ee4efb62c..6dd95d4e8 100644
--- a/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-parser-warnings/readme.txt
+++ b/tests/phpunit/testdata/plugins/test-plugin-plugin-readme-parser-warnings/readme.txt
@@ -1,7 +1,7 @@
 
 === Test Plugin Readme Errors Parser Warnings ===
 
-Contributors:      plugin-check
+Contributors:      plugin check, wordpressdotorg
 Requires at least: 6.0
 Tested up to:      Latest
 Requires PHP:      5.6
diff --git a/tests/phpunit/tests/Checker/Checks/Plugin_Readme_Check_Tests.php b/tests/phpunit/tests/Checker/Checks/Plugin_Readme_Check_Tests.php
index d2d4e06b4..73c63a97f 100644
--- a/tests/phpunit/tests/Checker/Checks/Plugin_Readme_Check_Tests.php
+++ b/tests/phpunit/tests/Checker/Checks/Plugin_Readme_Check_Tests.php
@@ -221,6 +221,7 @@ public function test_run_md_with_errors() {
 		$this->assertCount( 1, wp_list_filter( $warnings['readme.md'][0][0], array( 'code' => 'invalid_license' ) ) );
 		$this->assertCount( 1, wp_list_filter( $warnings['readme.md'][0][0], array( 'code' => 'license_mismatch' ) ) );
 		$this->assertCount( 1, wp_list_filter( $warnings['readme.md'][0][0], array( 'code' => 'mismatched_plugin_name' ) ) );
+		$this->assertCount( 1, wp_list_filter( $warnings['readme.md'][0][0], array( 'code' => 'readme_invalid_contributors' ) ) );
 	}
 
 	public function test_single_file_plugin_without_error_for_trademarks() {
@@ -479,4 +480,17 @@ public function test_run_with_errors_tested_up_to_latest_stable_version() {
 
 		delete_transient( 'wp_plugin_check_latest_wp_version' );
 	}
+
+	public function test_run_without_errors_readme_contributors_warning() {
+		$readme_check  = new Plugin_Readme_Check();
+		$check_context = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-plugin-readme-parser-warnings/load.php' );
+		$check_result  = new Check_Result( $check_context );
+
+		$readme_check->run( $check_result );
+
+		$warnings = $check_result->get_warnings();
+
+		// Should not contain contributors warning.
+		$this->assertCount( 0, wp_list_filter( $warnings['readme.txt'][0][0], array( 'code' => 'readme_invalid_contributors' ) ) );
+	}
 }