McMaster carried a 10-9 lead into the halftime break thanks to a 15-yard touchdown pass from QB Andreas Dueck to receiver Nicholas Adair at 9:02 of the first quarter, and a 10-yard field goal by kicker Michael Horvat.
The Varsity Blues countered with three field goals by Samuel Henke from 27, 18 and 11 yards out.
Toronto scored the only points of the second half, both of them safeties in the third quarter, to seal the victory.
It was McMaster’s first loss against the U of T since Sept. 21, 1996, a span of 26 years.
Mac ended the 2022 OUA football season with a record of 2-6, the first time the Marauders have finished with a sub-500 record since 1997. That year also marked the last time McMaster failed to make the playoffs in an eight-game season.