Gomez, 22, turned heads at the annual fashion bash in a custom ivory silk crepe Vera Wang Collection gown with a plunging back and black tassel detailing.
She accessorised with platinum jewelry by Lorraine Schwartz and an ornate white flowered headpiece, reported Us magazine.
Bieber, 21, before leaving the event in his car, yelled out the window, "Hey, Selena looked gorgeous at the Met Ball!"
He, meanwhile, sported a Balmain velvet blazer with golden dragon embroidery, which he teamed with black pants, a black shirt, and a black cummerbund.