 He successively served as assistant to Wiljan Vloet at Sparta Rotterdam for two seasons.In April 2011 Vonk agreed to return at Sparta as head coach for the 2011–12 season under supervision of newly appointed technical director Wiljan Vloet, who accepted to return at the Rotterdam club after two seasons as trainer of NEC Nijmegen.He was fired after one season.In July 2014, he started working for Telstar.