Posada's two-run homer in the ninth capped the scoring for the Yankees, who have won four in a row.
Alex Rodriguez had two hits -- one a solo homer -- and two RBI, and Melky Cabrera had two hits and one RBI.
Hideki Matsui had one RBI and a run scored on Travis Snider's first-inning error.
The winner was reliever Alfredo Aceves (10-1).
Toronto's Raul Chavez had three hits and two RBI.
Aaron Hill had one RBI.
A run scored on a sixth-inning error by Rodriguez and Snider added two hits for the Blue Jays, who have lost four in a row.
Losing pitcher Ricky Romero (11-7) gave up seven runs -- five earned -- and six hits in 4 1/3 innings with six walks and seven strikeouts.
Copyright 2009 by United Press International.