Brown, whose real name is Inga Marchand, tried to withdraw her guilty plea, but a judge said the agreement was legitimate and imposed the sentence.
"I'm innocent," the 27-year-old rapper argued Tuesday before Judge Melissa C. Jackson, claiming she felt rushed at the time she made the plea agreement. She also said her previous lawyer had told her she would face jail time unless she agreed to the deal.
Jackson rejected the appeal for a two-week extension and new arguments, instead handing down the sentence worked out in earlier negotiations.
"The purpose of a reargument is not to let the parties go over issues that have already been decided," Jackson said. She warned Brown that if she didn't abide by the conditions of her probation, she faced a possible sentence of one year in jail.
Brown pleaded guilty to misdemeanor assault charges in August for kicking one employee and smacking a second worker in the face on Aug. 29, 2004, in an argument over payment for a manicure at Bloomie Nails.
During the course of the trial, Brown hired three attorneys, tried once before to reverse her guilty plea and was threatened with jail time for missing a court appearance Monday. An earlier effort to reach a plea bargain last December had also fallen through.
Brown's albums include "Ill Na Na" and "Chyna Doll."