The singer and bodyguard Christopher Hollosy were allegedly involved in an altercation with another man outside the W Hotel at 4:25 a.m., police said.
The two were taken into custody and were being held at the 2nd District police station, police said.
The alleged victim was taken to a hospital for treatment of injuries, police spokesman Anthony Clay told CNN.
Brown, 24, was in Washington to host a “homecoming party” at The Park at Fourteen nightclub Saturday night, according to his Twitter feed, just four blocks away from where he was arrested Sunday morning.
His representative and lawyer did not immediately respond to CNN calls for comment Sunday.
Brown is on probation in California for a felony domestic violence conviction involving his former girlfriend Rihanna. Any arrest could be considered a violation of that probation, which could result in jail time.
Prosecutors filed probation violation charges against him twice in the past year, resulting in the judge ordering him to complete an additional 1,000 hours of community service.
Brown was arrested in February 2009 for punching Rihanna inside a rented Lamborghini on a Hollywood street. The altercation left the face of Rihanna, also a chart-topping singer, bruised and bloody on the eve of the Grammy Awards.
He entered a guilty plea seven months later and was sentenced to serve five years probation and ordered to spend more than 1,400 hours in “labor-oriented service.”
His probation reports were glowing until the past year, when the district attorney’s office accused him of not completing the 1,400 hours of community labor, which he was allowed to do in his home state of Virginia.
He was also accused of hit-and-run following a minor traffic crash earlier this year. The driver of the other car told investigators that Brown “went ballistic” and screamed at her after his Range Rover rear-ended her Mercedes on a Los Angeles street.
In August, Brown’s lawyer reached a settlement with prosecutors to end their efforts to revoke his probation. The deal called for Brown to complete another 1,000 hours of community service.
Probation rules require Brown to stay out of all legal trouble. Even an arrest that does not lead to a conviction could result in a probation violation charge.
He is scheduled to appear before Los Angeles County Superior Court Judge James Brandlin on November 20 for a probation status hearing.