Major League Soccer made the announcement Thursday in a release.
Olsen, a five-time MLS All-Star and the league's rookie of the year in 1998, has led United to a 9-4-3 start this season. United is in first place in the Eastern Conference, holding a slim one-point lead over Sporting Kansas City.
Olsen called it a "huge honor."
Serving as assistant coaches under Olsen will be Philadelphia Union interim manager John Hackworth, and the D.C. United technical staff of Chad Ashton, Pat Onstad and Sonny Silooy.
The All-Star match will be held at PPL Park in Chester, Pa.