"I'm sorry, I am very sorry," Brown told the judge in the brief hearing in a District of Columbia court.
The judge sentenced Brown, 25, to time served -- the one day he was locked up after his arrest -- and no probation for the simple assault conviction. He must also pay a $150 fine.
The singer has already paid a heavy price for the incident -- it resulted in the revocation of his probation for the 2009 beating of ex-girlfriend Rihanna in Los Angeles. He spent five months in court-ordered rehab and another three months in jail because of it.
His jail time also included two grueling cross-country trips on the federal government's "Con Air" inmate transport system.
A doctor's letter included in a probation report said that Brown was diagnosed as bipolar, which is blamed for violent outbursts.
"Mr. Brown has made significant strides in maintaining his sobriety, as well as developing skills that promote personal growth," a psychiatrist wrote in the most recent report in August.
He is taking his twice-a-week court-ordered psychological therapy sessions seriously, the doctor said.
"He continues to show great perseverance in implementing recommendations made by his treatment team, utilizing his learned skills and seeking guidance in his recovery process," his doctor reported.
Brown's probation officer said he has been "working on personal growth" and has been "taking responsibility for his behaviors" in the two months since he was freed from jail.
His probation for the 2009 felony battery conviction is expected to end on January 23, 2015, as long as he stays out of legal trouble and completes another 600 hours of community labor, the probation officer said last month.
The singer will spend three days each week until then working on a community labor crew.
Brown was a teenager when his remarkable dancing and singing talents made him a pop star. He was 19 when he smashed Rihanna's face with his fist during an argument inside a rented Lamborghini on the evening of the 2009 Grammy Awards.
With his legal troubles and probation requirements apparently nearing an end, Brown should have more time to concentrate on his career. He has a new album set to release this month, and he has teased fans with a Twitter post that suggested he would soon start a concert tour.
CNN's Lindy Royce contributed to this report.