The 'Girl on Fire' star took to the field of the Mercedes-Benz Superdome in New Orleans on Sunday (February 3).
Wearing a red dress and accompanied only by her white Yamaha piano, Keys sang the song to images of players, football fans and members of the military.
Prior to performing, Keys wrote on her official Twitter account: "Getting ready to sing my heart out for America! The city is electric!!"
Keys's rendition of the song was distinctly slower in tempo than usual, according to SBNation, with 38 seconds added to the two-minute song.
Jennifer Hudson also performed during the opening of the sporting event, accompanied by the children's chorus of the Sandy Hook Elementary School.
Watch Keys sing the American National Anthem below: