diff --git a/src/Admin/ConnectionTestController.php b/src/Admin/ConnectionTestController.php
new file mode 100644
index 0000000..598da3c
--- /dev/null
+++ b/src/Admin/ConnectionTestController.php
@@ -0,0 +1,100 @@
+<?php
+/**
+ * Handles admin REST connection diagnostics.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Admin;
+
+use WPContentSync\Logging\LoggerInterface;
+use WPContentSync\Settings\SettingsRepository;
+use WPContentSync\Transport\RestTransportClient;
+use WPContentSync\Transport\RestTransportException;
+
+final class ConnectionTestController {
+	private SettingsRepository $settings_repository;
+
+	private RestTransportClient $transport_client;
+
+	private LoggerInterface $logger;
+
+	public function __construct(
+		SettingsRepository $settings_repository,
+		RestTransportClient $transport_client,
+		LoggerInterface $logger
+	) {
+		$this->settings_repository = $settings_repository;
+		$this->transport_client    = $transport_client;
+		$this->logger              = $logger;
+	}
+
+	public function register(): void {
+		add_action( 'admin_post_wpcs_test_connection', array( $this, 'handleTest' ) );
+	}
+
+	public function handleTest(): void {
+		if ( ! current_user_can( 'manage_options' ) ) {
+			throw new \RuntimeException( 'You do not have permission to test WP Content Sync connections.' );
+		}
+
+		if ( ! check_admin_referer( 'wpcs_test_connection', 'wpcs_connection_nonce' ) ) {
+			throw new \RuntimeException( 'The connection test request could not be verified.' );
+		}
+
+		// phpcs:ignore WordPress.Security.NonceVerification.Missing -- Nonce verified above.
+		$pair_index = isset( $_POST['pair_index'] ) ? max( 0, (int) sanitize_text_field( wp_unslash( $_POST['pair_index'] ) ) ) : 0;
+		$pairs      = $this->settings_repository->get()->syncPairs();
+		$pair       = $pairs[ $pair_index ] ?? null;
+
+		if ( ! is_array( $pair ) ) {
+			$this->redirectWithError( 'The selected sync pair could not be found.' );
+			return;
+		}
+
+		try {
+			$this->transport_client->testConnection(
+				(string) $pair['destination_url'],
+				(string) $pair['username'],
+				(string) $pair['application_password']
+			);
+
+			$this->logger->info(
+				'REST connection test succeeded.',
+				array(
+					'pair_index'      => $pair_index,
+					'destination_url' => (string) $pair['destination_url'],
+					'username'        => (string) $pair['username'],
+				)
+			);
+
+			wp_safe_redirect(
+				add_query_arg(
+					array( 'wpcs_connection_ok' => '1' ),
+					admin_url( 'admin.php?page=wp-content-sync' )
+				)
+			);
+		} catch ( RestTransportException $exception ) {
+			$this->logger->warning(
+				'REST connection test failed.',
+				array(
+					'pair_index'      => $pair_index,
+					'destination_url' => (string) $pair['destination_url'],
+					'username'        => (string) $pair['username'],
+					'failure_code'    => $exception->failureCode(),
+				)
+			);
+
+			$this->redirectWithError( $exception->getMessage() );
+		}
+	}
+
+	private function redirectWithError( string $message ): void {
+		wp_safe_redirect(
+			add_query_arg(
+				array( 'wpcs_connection_error' => sanitize_text_field( $message ) ),
+				admin_url( 'admin.php?page=wp-content-sync' )
+			)
+		);
+	}
+}
diff --git a/src/Plugin.php b/src/Plugin.php
index b37c33c..243b7e4 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -8,6 +8,7 @@
 namespace WPContentSync;
 
 use WPContentSync\Admin\AdminPage;
+use WPContentSync\Admin\ConnectionTestController;
 use WPContentSync\Admin\FileImportController;
 use WPContentSync\Admin\SettingsController;
 use WPContentSync\Content\ContentHandlerRegistry;
@@ -186,6 +187,17 @@ final class Plugin {
 			}
 		);
 
+		$container->factory(
+			ConnectionTestController::class,
+			static function () use ( $container ): ConnectionTestController {
+				return new ConnectionTestController(
+					$container->get( SettingsRepository::class ),
+					$container->get( RestTransportClient::class ),
+					$container->get( LoggerInterface::class )
+				);
+			}
+		);
+
 		$container->factory(
 			RestPackageController::class,
 			static function () use ( $container ): RestPackageController {
@@ -222,9 +234,13 @@ final class Plugin {
 		/** @var SettingsController $settings_controller */
 		$settings_controller = $this->container->get( SettingsController::class );
 
+		/** @var ConnectionTestController $connection_test_controller */
+		$connection_test_controller = $this->container->get( ConnectionTestController::class );
+
 		$admin_page->register();
 		$file_import_controller->register();
 		$rest_package_controller->register();
 		$settings_controller->register();
+		$connection_test_controller->register();
 	}
 }
diff --git a/templates/admin/dashboard.php b/templates/admin/dashboard.php
index 8c405ea..b93d458 100644
--- a/templates/admin/dashboard.php
+++ b/templates/admin/dashboard.php
@@ -51,6 +51,20 @@ if ( array() === $sync_pairs ) {
 		</div>
 	<?php endif; ?>
 
+	<?php // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Displays redirect status only. ?>
+	<?php if ( isset( $_GET['wpcs_connection_ok'] ) ) : ?>
+		<div class="notice notice-success">
+			<p><?php echo esc_html__( 'REST connection succeeded.', 'wp-content-sync' ); ?></p>
+		</div>
+	<?php endif; ?>
+
+	<?php // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Displays redirect status only. ?>
+	<?php if ( isset( $_GET['wpcs_connection_error'] ) ) : ?>
+		<div class="notice notice-error">
+			<p><?php echo esc_html( sanitize_text_field( wp_unslash( $_GET['wpcs_connection_error'] ) ) ); ?></p>
+		</div>
+	<?php endif; ?>
+
 	<h2><?php echo esc_html__( 'Configuration', 'wp-content-sync' ); ?></h2>
 	<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>">
 		<input type="hidden" name="action" value="wpcs_save_settings" />
@@ -176,6 +190,26 @@ if ( array() === $sync_pairs ) {
 		<?php submit_button( __( 'Save Settings', 'wp-content-sync' ) ); ?>
 	</form>
 
+	<h2><?php echo esc_html__( 'Connection Diagnostics', 'wp-content-sync' ); ?></h2>
+	<p><?php echo esc_html__( 'Test whether each configured destination site accepts REST requests with the saved application password.', 'wp-content-sync' ); ?></p>
+	<?php foreach ( $sync_pairs as $index => $pair ) : ?>
+		<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>">
+			<input type="hidden" name="action" value="wpcs_test_connection" />
+			<input type="hidden" name="pair_index" value="<?php echo esc_attr( (string) $index ); ?>" />
+			<?php wp_nonce_field( 'wpcs_test_connection', 'wpcs_connection_nonce' ); ?>
+			<p>
+				<?php
+				printf(
+					/* translators: %s: sync pair name. */
+					esc_html__( 'Pair: %s', 'wp-content-sync' ),
+					esc_html( '' !== $pair['name'] ? $pair['name'] : __( 'Unnamed sync pair', 'wp-content-sync' ) )
+				);
+				?>
+			</p>
+			<?php submit_button( __( 'Test REST Connection', 'wp-content-sync' ), 'secondary' ); ?>
+		</form>
+	<?php endforeach; ?>
+
 	<h2><?php echo esc_html__( 'File Package Import', 'wp-content-sync' ); ?></h2>
 	<form method="post" action="<?php echo esc_url( admin_url( 'admin-post.php' ) ); ?>" enctype="multipart/form-data">
 		<input type="hidden" name="action" value="wpcs_import_package" />
diff --git a/tests/Unit/Admin/ConnectionTestControllerTest.php b/tests/Unit/Admin/ConnectionTestControllerTest.php
new file mode 100644
index 0000000..1fe3b85
--- /dev/null
+++ b/tests/Unit/Admin/ConnectionTestControllerTest.php
@@ -0,0 +1,106 @@
+<?php
+/**
+ * Tests for admin REST connection diagnostics.
+ *
+ * @package WPContentSync
+ */
+
+namespace WPContentSync\Tests\Unit\Admin;
+
+use PHPUnit\Framework\TestCase;
+use WPContentSync\Admin\ConnectionTestController;
+use WPContentSync\Logging\OptionLogger;
+use WPContentSync\Settings\SettingsRepository;
+use WPContentSync\Transport\RestTransportClient;
+
+class ConnectionTestControllerTest extends TestCase {
+	protected function tearDown(): void {
+		unset(
+			$GLOBALS['wpcs_current_user_can'],
+			$GLOBALS['wpcs_nonce_valid'],
+			$GLOBALS['wpcs_redirect_location'],
+			$GLOBALS['wpcs_test_options'],
+			$GLOBALS['wpcs_test_option_autoloads'],
+			$GLOBALS['wpcs_http_response'],
+			$GLOBALS['wpcs_last_http_request']
+		);
+
+		$_POST = array();
+
+		parent::tearDown();
+	}
+
+	public function test_it_tests_a_configured_pair_with_nonce_and_capability(): void {
+		$this->storePair();
+		$GLOBALS['wpcs_current_user_can']['manage_options']                           = true;
+		$GLOBALS['wpcs_nonce_valid']['wpcs_test_connection']['wpcs_connection_nonce'] = true;
+		$_POST['pair_index'] = '0';
+
+		$this->controller()->handleTest();
+
+		self::assertStringContainsString( 'wpcs_connection_ok=1', $GLOBALS['wpcs_redirect_location'] );
+		self::assertSame( 'GET', $GLOBALS['wpcs_last_http_request']['method'] );
+		self::assertSame( 'https://destination.test/wp-json/wp-content-sync/v1/status', $GLOBALS['wpcs_last_http_request']['url'] );
+	}
+
+	public function test_it_rejects_users_without_manage_options(): void {
+		$GLOBALS['wpcs_current_user_can']['manage_options'] = false;
+
+		$this->expectException( \RuntimeException::class );
+		$this->expectExceptionMessage( 'You do not have permission to test WP Content Sync connections.' );
+
+		$this->controller()->handleTest();
+	}
+
+	public function test_it_rejects_invalid_nonces(): void {
+		$GLOBALS['wpcs_nonce_valid']['wpcs_test_connection']['wpcs_connection_nonce'] = false;
+
+		$this->expectException( \RuntimeException::class );
+		$this->expectExceptionMessage( 'The connection test request could not be verified.' );
+
+		$this->controller()->handleTest();
+	}
+
+	public function test_it_redirects_failures_without_leaking_application_passwords(): void {
+		$this->storePair();
+		$GLOBALS['wpcs_current_user_can']['manage_options']                           = true;
+		$GLOBALS['wpcs_nonce_valid']['wpcs_test_connection']['wpcs_connection_nonce'] = true;
+		$GLOBALS['wpcs_http_response'] = array(
+			'response' => array( 'code' => 401 ),
+			'body'     => '{"message":"Unauthorized"}',
+		);
+		$_POST['pair_index']           = '0';
+
+		$this->controller()->handleTest();
+
+		self::assertStringContainsString( 'wpcs_connection_error=', $GLOBALS['wpcs_redirect_location'] );
+		self::assertStringNotContainsString( 'app-pass', $GLOBALS['wpcs_redirect_location'] );
+		self::assertStringNotContainsString( 'app-pass', wp_json_encode( $GLOBALS['wpcs_test_options'][ OptionLogger::OPTION_NAME ] ) );
+	}
+
+	private function controller(): ConnectionTestController {
+		return new ConnectionTestController(
+			new SettingsRepository(),
+			new RestTransportClient(),
+			new OptionLogger()
+		);
+	}
+
+	private function storePair(): void {
+		update_option(
+			SettingsRepository::OPTION_NAME,
+			array(
+				'sync_pairs' => array(
+					array(
+						'name'                 => 'Staging',
+						'source_url'           => 'https://source.test',
+						'destination_url'      => 'https://destination.test',
+						'username'             => 'codex',
+						'application_password' => 'app-pass',
+					),
+				),
+			),
+			false
+		);
+	}
+}
diff --git a/tests/Unit/Admin/DashboardTemplateTest.php b/tests/Unit/Admin/DashboardTemplateTest.php
index 6acfc5e..eef6562 100644
--- a/tests/Unit/Admin/DashboardTemplateTest.php
+++ b/tests/Unit/Admin/DashboardTemplateTest.php
@@ -55,6 +55,27 @@ class DashboardTemplateTest extends TestCase {
 		self::assertStringContainsString( 'name="wpcs_settings[sync_pairs][0][url_mappings][0][source]"', $output );
 	}
 
+	public function test_it_renders_connection_diagnostics_for_each_pair(): void {
+		$settings = Settings::fromArray(
+			array(
+				'sync_pairs' => array(
+					array(
+						'name'            => 'Staging',
+						'destination_url' => 'https://staging.example.test',
+						'username'        => 'codex',
+					),
+				),
+			)
+		);
+
+		$output = $this->renderDashboard( $settings );
+
+		self::assertStringContainsString( 'name="action" value="wpcs_test_connection"', $output );
+		self::assertStringContainsString( 'name="wpcs_connection_nonce"', $output );
+		self::assertStringContainsString( 'name="pair_index" value="0"', $output );
+		self::assertStringContainsString( 'Test REST Connection', $output );
+	}
+
 	private function renderDashboard( ?Settings $settings = null ): string {
 		$settings = $settings ?? Settings::fromArray( array() );
 
diff --git a/tests/Unit/PluginTest.php b/tests/Unit/PluginTest.php
index 99db60a..1c0d509 100644
--- a/tests/Unit/PluginTest.php
+++ b/tests/Unit/PluginTest.php
@@ -4,6 +4,7 @@ namespace WPContentSync\Tests\Unit;
 
 use PHPUnit\Framework\TestCase;
 use WPContentSync\Admin\FileImportController;
+use WPContentSync\Admin\ConnectionTestController;
 use WPContentSync\Admin\SettingsController;
 use WPContentSync\Content\ContentHandlerRegistry;
 use WPContentSync\Content\ContentRecordNormalizer;
@@ -61,6 +62,15 @@ class PluginTest extends TestCase {
 		);
 	}
 
+	public function test_it_registers_connection_test_controller(): void {
+		$container = $this->getPluginContainer( Plugin::create() );
+
+		self::assertInstanceOf(
+			ConnectionTestController::class,
+			$container->get( ConnectionTestController::class )
+		);
+	}
+
 	public function test_it_registers_rest_transport_services(): void {
 		$container = $this->getPluginContainer( Plugin::create() );
 
@@ -104,6 +114,15 @@ class PluginTest extends TestCase {
 		self::assertArrayHasKey( 'admin_post_wpcs_save_settings', $GLOBALS['wpcs_test_actions'] );
 	}
 
+	public function test_it_hooks_connection_test_controller_on_register(): void {
+		unset( $GLOBALS['wpcs_test_actions'] );
+
+		$plugin = Plugin::create();
+		$plugin->register();
+
+		self::assertArrayHasKey( 'admin_post_wpcs_test_connection', $GLOBALS['wpcs_test_actions'] );
+	}
+
 	private function getPluginContainer( Plugin $plugin ): Container {
 		$reflection = new \ReflectionClass( $plugin );
 		$property   = $reflection->getProperty( 'container' );