Mariah, 49, posed happily for the cameras before making her way inside Madison Square Garden.
She dazzled in a form fitting black dress that came with a ton of sparkly accessories.
Her gorgeous locks appeared windswept during the big night.
The "Touch My Body" singer posted plenty of Instagram stories while there. She lip synced to Barbra's classic "The Way We Were" at one point.
Other's celebs at Barbra's show included The View cohost Whoopi Goldberg and comedian Rosie O'Donnell.
Barbra, 77, is known for attracting A-list stars at her sold out concerts.
David and Victoria Beckham were spotted at her London show on Sunday, July 7.
Pitch Perfect actress Rebel Wilson was at the same show enjoying an ice cream cone during Barbra's performance.