The 'Faith' hitmaker will star alongside Alicia, Tinie Tempah and Paloma Faith at the event on June 15, which will raise funds for the charity, which works to improve the life of families affected by AIDS.
Commenting on George's addition to the bill, Alicia said: "I've been a fan of George Michael for as long I can remember. He is a legend and an inspiration.
"I'm honoured that George has lent his voice to our Keep a Child Alive cause and I'm so excited that he's singing for us at the Black Ball in London. It's going to be an amazing night!"
George, 47, recently announced his return to live performance since 'retiring' in 2008, and will play across Europe backed by a symphony orchestra this summer.
Speaking of his return, he said: "More than anything it's such an amazing thing to watch the effect on my audience that an evening's entertainment has on them.
"It seems God wanted me to, he gave me the voice to do it and the stamina to do it at my age. I thought, it is the most positive experience I've had in the last 20 years, so why wait?"
The fourth annual Black Ball London will take place at the city's Roundhouse venue on June 15. For tickets or information visit www.keepachildalive.org/the-black-ball