They were seen together at singer Rihanna's Met Gala (an annual fundraising gala for the benefit of the Metropolitan Museum of Art's Costume Institute here) after-party on Monday.
The duo stayed at the venue until "three or four in the morning". Sources told the New York Post newspaper's Page Six column that Cooper and Shayk started the night "hanging out in a close group" with Kerry Washington, Leonardo DiCaprio and Tyler Winklevoss, but then slipped downstairs into "the karaoke room", where "they were making out", reports femalefirst.co.uk.
"They were very close all night," the source added.
Also at the club dancing in one group, were singers Rihanna, Madonna and supermodel Naomi Campbell. They were later joined by P.Diddy, Miley Cyrus, Jennifer Lawrence and Madonna's 18-year-old daughter Lourdes
"It was insane. It was a dance-party circle of superstardom," said a source.