Growing up in Maxville, Ontario the son of Dutch immigrants, Wensink is best remembered for his time with the Boston Bruins, where he teamed with Terry O'Reilly and Stan Jonathan as the team's enforcers. In one of the most infamous moments in National Hockey League history, on December 1, 1977, Wensink, after just fighting Alex Pirus of the Minnesota North Stars, skated over to the Minnesota bench and motioned with his hands, challenging the entire team but no player responded. Wensink is also well known for his large afro that he sported on the ice. In another scrap with Bob Kelly (another 1970s hockey player with an afro), Wensink and Kelly were pulling at each other's hair.
Besides his skill as a fighter, Wensink also could score as well. He had a career high 46 points in the 1978/79 season for the Bruins.
Currently, John Wensink continues to play hockey in a Sunday night men's league at the Hardee's Iceplex in Chesterfield, MO.