The Bucks acquired Allen from the Memphis Grizzlies in a trade this summer. The deal happened ahead of the 6 p.m. ET deadline for members of the 2018 NBA draft to sign extensions.
Allen, the 21st pick in 2018, set career highs in points (10.6), rebounds (3.2) and assists (2.2) per game last season for a Memphis team that advanced from the play-in tournament to become the eighth seed in the Western Conference playoffs.
The former Duke standout also shot 39.1% from 3-point range while averaging 25.2 minutes per game.
Allen's addition helps the defending NBA champion Bucks fill the long-distance void left by Bryn Forbes, who declined his player option and signed with the Spurs in free agency.