Despite being hired late in the off-season, Trestman's first season in Toronto went above expectations, given the circumstances. Trestman inherited a roster that finished last in the league the previous season, and guided the team to a 9–9 record, which was good enough for first place in the East and a first-round bye in the playoffs. On Sunday, November 26, 2017, Trestman won his third Grey Cup when the Argonauts defeated the Stampeders 27–24. During that season he won the Annis Stukus Trophy and was named CFL coach of the year.