UsMagazine.com reported an attorney entered the plea on the 43-year-old New Edition singer's behalf Wednesday.
Brown was sentenced to three years' probation and a day in Los Angeles County jail but he received credit for time served and will not spend any more time behind bars, the Web site said.
Brown was arrested March 26 after police pulled him over for driving while talking on his cellphone. Police said he appeared intoxicated and failed a field sobriety test.
Brown's ex-wife, singer Whitney Houston, accidentally drowned in a hotel bathtub the month before Brown's arrest. She was 48 when she died after years of drug abuse.