In return, the Grizzlies will get guard Sam Merrill and two future second-round picks, sources said.
Allen, the 25-year-old former Duke standout, set career highs in points (10.6), rebounds (3.2) and assists (2.2) per game this season for a Memphis team that advanced from the play-in tournament to become the eighth seed in the Western Conference playoffs.
The 6-foot-4 guard also shot 39.1% from 3-point range while averaging 25.2 minutes per game. Allen’s addition may help the NBA champion Bucks fill the long-distance void left by Bryn Forbes, who declined his player option and became an unrestricted free agent.
Merrill, a second-round pick in last year’s draft, averaged 7.8 minutes per game while appearing in 30 games for Milwaukee, starting two.