City attorney's spokesman Frank Mateljan (mah-TEHL'-jin) says the pleas were entered Friday. Brown's case is scheduled for its next hearing on Dec. 13.
Brown was arrested in October on suspicion of driving while under the influence. It was his second arrest for DUI this year in Los Angeles.
He also faces charges he was driving on a suspended license and did not have an ignition locking device on his car, as required from a previous case.
Brown pleaded no contest to drunken driving in April and entered rehab in August.
The 43-year-old is the former husband of Whitney Houston.