Cecil was called up to the Toronto Blue Jays on May 1, 2009, and made his major league debut on May 5 as the starting pitcher against the Cleveland Indians at home. In that game, Cecil pitched six innings, giving up two runs, one earned, and six hits but was credited with a no-decision in a game Toronto eventually won. His next start was May 10 against the Oakland Athletics, pitching 8 scoreless innings to earn his first Major League win. Cecil defeated the Chicago White Sox, keeping Toronto in first place, but then gave up five home runs to the Boston Red Sox on May 21, losing his first game, as Toronto went on a nine-game losing streak and dropped out of first place. Cecil was returned to AAA after losing to Boston, and then pitched solidly for the Las Vegas 51s. Continued injury problems for Blue Jays' pitchers led to Cecil being recalled to the major leagues on June 18, and he started against the Washington Nationals on June 20, filling in for the injured Casey Janssen and Roy Halladay, pitching 7 innings while allowing 3 earned runs in a no-decision, in a game Toronto lost in 12 innings.