Actor Mitchy Collins, who was also a guest at the star-studded affair, captured video on his Instagram Stories of Cabello, 22, Mendes, 21, Horan, 26, and Capaldi, 23, dancing and singing on a bar inside the 40 Love venue in West Hollywood.
“I love them all,” Collins captioned a clip of the group singing to Capaldi’s hit “Someone You Loved,” which was nominated for Song of the Year earlier that night. Billie Eilish took home the honor for “Bad Guy.”
YouTube star Tana Mongeau also attended the party, and snagged video of Cabello, Mendes and Capaldi singing “Steal My Girl” by Horan’s former boy band “One Direction.”
Like Capaldi, Cabello and Mendes were nominated earlier in the night.
The couple were up for Best Pop Duo/Group Performance for their duet, “Señorita.” Lil Nas X and Billy Ray Cyrus won in that category for their “Old Town Road” remix.
Despite not winning, Cabello had a successful night, performing twice on the Grammys stage.
She debuted her song “First Man” and performed a number from “Fame” with other stars.
After a long night of dancing and singing, the pop star was seen leaving 40 Love holding hands with Mendes.
The pair have been dating since July 2018.