Gilbert Arenas scored 24 points in the absence of John Wall and Washington handed the Grizzlies their fifth straight setback. Wall missed his third straight game with a sprained left foot and the Wizards were also without center Yi Jianlian (bruised knee).
Arenas missed a layup with 51 seconds to play but McGee grabbed the offensive rebound and slammed it home for an 89-85 lead.
Marc Gasol hit 1-of-2 free throws for Memphis with 37 seconds left and the Grizzlies regained the ball with plenty of time to hit a tying field goal. O.J. Mayo and Mike Conley, however, both missed 3-point attempts.
Kirk Hinrich added 22 points for Washington. Memphis was led by 19 points and 12 rebounds by Zach Randolph.