In the 2020 season he was 5-1 with a 4.08 ERA. He tied for the AL lead in wild pitches, with seven. In the postseason, Glasnow started the clinching game in both the Wild Card round (Blue Jays) and Division Series (Yankees). In Game 5 of the ALDS, he started the game on two days' rest. This was the second straight year Glasnow started the fifth game of the ALDS for the Rays; both times he faced off against his former teammate Gerrit Cole. Glasnow became the second pitcher since 1980 to start a game on two days' rest. He started Game 1 of the World Series against the Los Angeles Dodgers, taking the loss after giving up six walks and six earned runs in innings.