Brown, 19, was arrested Feb. 8 after he allegedly left Rihanna, 21, bloody and bruised during a heated argument in a car.
Usmagazine.com said Brown's lawyer, Mark Geragos, entered not guilty pleas at Brown's arraignment on felony charges of assault and making criminal threats.
Brown is due back in court April 29.
Rihanna reportedly was in her native Barbados Monday. Her attorney, Donald Etra, has said the singer will testify against Brown if required to do so by law.
The couple reconciled shortly after the alleged incident. However, they reportedly have been spending time apart in recent weeks.