Jackson, 48, arrived at the party hand-in-hand with her husband, 39, wearing a hooded blazer with black pants and black platform sandals, reported People magazine.
The star-studded event was also attended by Tom Cruise, Sophia Loren, and Tina Turner.
Before this rare sighting, the "That's the Way Love Goes" singer had not been spotted since February, when she was photographed shopping for shoes in Milan.