The 26-year-old 'Stay' hitmaker will perform at the gala, which benefits Rihanna's Clara Lionel Foundation (CLF) and takes place on December 11, reported E! Online.
Comedian Jimmy Kimmel will host the soiree.
"It is such an honor to have Jimmy Kimmel host this event. There is no one more hilarious to make the first annual Diamond Ball an incredible night. I'm blessed by his support. Brad Pitt is not only a phenomenal talent, but I admire him and am inspired by his philanthropic work," Rihanna said in a statement.
The Diamond Ball's proceeds will help finance the Center's USD 2.4 million improvement initiative.
The event for about 600 guests will take place at the private 157-acre The Vineyard in Beverly Hills.
