The gun-possession case stems from a July 2007 stop of his luxury sports car. The rapper said "this isn't a good day" and declined to discuss the case as he left a Manhattan court.
Police say they found a loaded semiautomatic gun in a rear door of the $250,000-plus car after it was stopped for speeding.
In court Monday, Ja Rule was promised a two-year prison sentence. He's free until sentencing, on a date yet to be set. He's due in court Feb. 9 for an update.
Ja Rule's "Pain is Love" was nominated for a best rap album Grammy Award in 2002. The 34-year-old rapper - born Jeffrey Atkins - also has appeared in movies, including the 2001 film "The Fast and the Furious."