They were "laughing and chatting" an eyewitness tells Us Weekly. The twosome, who sat courside together, "looked happy together," the source adds.
Rihanna, 24, wore a midriff-baring black top to the game and black pants. Brown, 23, also dressed in all black with a leather jacket.
The exes have been spending more time together recently and tweeting Instagram photos together. But the "We Found Love" singer alluded she was single on Twitter Dec. 18 by tweeting an E-card that read, "Being single sucks. The only thing I get to do anymore is whatever the f--k I want to do."