The festival said: "She sends her sincerest apologies, and looks forward to performing at Coachella in the future."
Solange was due to play on 13 and 20 April at the event in California that's known for its A-list guests and huge artists.
Last year she made a stage appearance during her sister Beyonce's iconic set.
This year's headliners are Childish Gambino, Tame Impala and Ariana Grande.
Acts like Diplo, Billie Eilish and The 1975 will also be performing.
Radio 1 Newsbeat has contacted representatives for Solange Knowles but no further information or comment has been made available.
Last month Solange released her fourth album, a follow-up to her 2016 critically acclaimed album A Seat at the Table which won her her first Grammy.