SHENZHEN, China—A Shenzhen real-estate developer with seemingly sound finances likely became one of the first Chinese property companies to default on offshore bonds Thursday, in a development that is raising concerns among global investors

Kaisa Group Holdings Ltd. appears to have missed interest payments due on $500 million of debt held by foreign investors, several managers of funds that hold the bonds said. Although the company has a 30-day grace period to pay after the due date, missing the deadline would put Kaisa in...