Powe gives the Grizzlies help at forward, where Rudy Gay remains out after dislocating his left shoulder Feb. 15.
The 6-foot-8 Powe averaged 5.0 points and 2.7 rebounds in 14 games for the Cleveland Cavaliers this season before he was waived Feb. 24.
He also brings playoff experience, serving as a key reserve for the Boston Celtics during their 2007-08 championship season.
Memphis now has three players with playoff experience as it makes a run at the postseason. The Grizzlies are eighth in the Western Conference, with a key game Monday against fourth-place Oklahoma City.
Gay is expected to miss at least a month. He is the team's leading scorer, averaging 19.8 points.