Chris Brown pleaded in guilty in court f or punching a man who tried to join a picture the singer was taking outside a hotel in Washington DC.
Brown walked free from the court after being sentenced to time served. He had already been in jail for two days in connection with the case.
He was arrested and charged with misdemeanor assault in October after the scuffle outside the W hotel.
The victim in the case said Brown hit him after he tried to get in a photograph the star was taking with two women.
Brown's bodyguard, Christopher Hollosy, was also charged in the same incident.
Hollosy was convicted of misdemeanor assault in April. He has not yet been sentenced.
Brown was on probation for assaulting Rihanna when he was arrested
Brown had previously pleaded not guilty in the case. His trial had been set for April, but it was delayed.
At the time of his Washington arrest, Brown was on probation in a felony assault case in California for attacking his then-girlfriend, pop star Rihanna, hours before the 2009 Grammy Awards.
Because Brown was still on probation, the outcome of his Washington case had potential repercussions in California.
During a court hearing in May, a Los Angeles judge sentenced Brown to serve an additional 131 days in jail. He was released in June.
Brown's lawyer, Danny Onorato, argued that Brown had already been punished extensively for the assault, noting the time he spent in jail in California and four months he spent receiving inpatient counselling after his probation was revoked.
Brown's lawyer said the case had put the star's career on hold
"To say that he's been punished severely in this matter is an understatement," Mr Onorato said.
He said Brown's career has been on hold for nearly a year and he wanted to take responsibility for his actions so he could go back to work, including a tour in support of a new album.
Brown spoke only briefly, saying: "I would like to say to the court that I'm sorry."
He did not comment as he left court, swarmed by photographers and a handful of fans.