The 6-foot-3 Howard is a California native who played the last three seasons for the Terps.
"We are happy that Pe'Shon will be able to spend time with his grandmother who helped raise him here in Los Angeles," Enfield said in a statement. "On the court, Pe'Shon will provide leadership and we expect him to have a terrific senior season."
Howard would have almost certainly been a reserve guard for Maryland coach Mark Turgeon this season, backing up Seth Allen and freshman Roddy Peters at the point guard position. Howard averaged 3.3 points and 3.6 assists while starting 24 games last season.
Now he becomes the frontrunner to start for a Trojans team that is expected to struggle in Enfield's first season since moving over from Florida Gulf Coast. The other options at the point at USC are walk-on Chass Bryan -- who backed up Jio Fontan last season -- and 6-foot-3 freshman combo guard Julian Jacobs.