The pair will headline the show at the House of Blues in Los Angeles on February 12, with proceeds going to the Children's Orthopaedic Centre and an artists' programme at the city's Children's Hospital.
MTV reports that producer deadmau5 and Swedish House Mafia's Sebastian Ingrosso will also perform at the event.
Harris said of his collaboration with Rihanna: "We Found Love' is the most successful thing I've done ever. It's not strictly a song by me, obviously, it's by Rihanna. She sings it.
"It was great to work with her. No-one could have taken it as far as she did. You can't escape it here [in America]. I've heard it a lot. I've heard it probably more times today than I did when I was mixing it, which is a good thing."
The gig is scheduled to take place on the same day as The Grammys, where Rihanna is due to perform with Coldplay.
The 'Umbrella' singer recently responded to criticism about her "thug life" tattoo, tweeting: "Err'body has an opinion, but yall know what yall can do with them!!! (sic)"
Watch the 'We Found Love' music video below: