The 35-year-old performer pleaded guilty in December to attempted weapon possession. He agreed to a two-year prison term.
Police say they found a loaded gun in a rear door of his luxury sports car when it was stopped for speeding after a July 2007 concert.
Ja Rule was nominated for a 2002 best rap album Grammy Award for "Pain is Love." His movie credits include 2001's "The Fast and the Furious" and 2003's "Scary Movie 3."