The Wizards announced before their game at the Toronto Raptors on Wednesday that Beal has a stress injury in his right fibula and is expected to resume basketball-related activities in about six weeks.
Washington has eight games left in the regular season. The Wizards are 28-46 entering Wednesday's game.
Beal, the No. 3 overall pick in last year's draft, averaged 13.9 points, 3.8 assists and 2.4 rebounds this season. He earned Eastern Conference rookie of the month honors in December and January.
Beal played 27½ minutes in Washington's 90-86 victory over Chicago on Tuesday night.