Brown sings on the remix of Rihanna's sexually charged song "Birthday Cake," and she's on the remix of his upbeat tune "Turn up the Music."
They tweeted links to the songs on Monday.
Brown is currently serving five years of probation after pleading guilty to a felony charge for attacking then-girlfriend Rihanna at a pre-Grammy Awards party in 2009.
Last year, a judge eased a restraining order after an attorney for Rihanna said she didn't object to reducing the stay-away provisions at music industry events.
Brown performed twice at the Grammys, winning best R&B album. Rihanna also performed and picked up a trophy.
The Associated Press contributed to this story.
