He finished the season with just 4 tries from 19 games, his lowest try tally since 2011. In Round 2 of the 2018 NRL season, Winterstein played his 200th NRL game. On 25 July 2018, after playing 16 games in the 2018 NRL season, Winterstein announced his retirement from rugby league, effective immediately, on advice from the club medical staff due to a persistent knee injury. Winterstein and his anti-vaxxer wife Brooke Winterstein (née Peninton) have four daughters, Milanah, Harlan, Novah and Finnlay. Winterstein comes from a very large rugby league family. His uncles are Paddy and Tony Tuimavave, and he is a cousin of Evarn Tuimavave, current Hull F.C. player Carlos and Manly Sea Eagles forward Frank Winterstein.