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.
Entering Wednesday, Washington was 28-46, with eight games left in the regular season.
Beal, the No. 3 overall pick in last year's draft out of Florida, 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 27 1/2 minutes in Washington's 90-86 victory over Chicago on Tuesday night, his second game back after missing time with a left ankle injury.
He had been bothered by the right leg, too, and an MRI exam Wednesday showed the stress injury.
Beal already had been sidelined for a total of 18 games this season: 11 because of the left ankle, five because of a sprained right wrist, and two because of a sore back.
When healthy, Beal and point guard John Wall -- the No. 1 overall pick in the 2010 draft -- gave the Wizards a glimpse of what could be their backcourt of the future.