Belisario, who was five weeks late reporting to camp due to visa issues, will be a welcome addition to the Dodgers' beleaguered bullpen.
Dodgers manager Joe Torre said Belisario is in excellent shape physically.
"He should be fine," Torre said. "I know he's excited to be back. He could go back-to-back [days] unless his pitch count is up."
Belisario, who has been working out at the Dodgers' Spring Training complex in Arizona, enjoyed a breakout rookie season in 2009, going 4-3 with a 2.04 ERA in 69 games.
Belisario learned of his impending activation on Monday and joined the team in Cincinnati a few hours before Wednesday night's game against the Reds.
"We've been just talking about what I have to do," Belisario said. "I'm pretty excited to be back. I've tried to prepare myself."
Jon Link, who made his big league debut with two scoreless innings of relief in Tuesday night's loss, was optioned to Triple-A Albuquerque to make room for Belisario.