The singer, 17, made her debut appearance on the NBC sketch comedy series for the season 45 premiere on Saturday night, hosted by Woody Harrelson.
Eilish performed her hit song “Bad Guy,” joined by her brother, Finneas O’Connell, who co-wrote the song with her. The sibling duo also performed a duet to their new single, “I Love You,” later in the show.
“Bad Guy” became Eilish’s first number-one single in the United States after the singer released it in March. She and O’Connell, 22, frequently collaborate on music.
It also marked the first episode for new cast members Chloe Finneman and Bowen Yang.
SNL has already confirmed Taylor Swift to perform on the show next week, which will be hosted by Emmy winner Phoebe Waller-Bridge. The Oct. 12 episode will feature Camila Cabello as the musical guest, with Stranger Things’ David Harbour as the host.
Saturday Night Live airs Saturdays at 11:30 p.m. ET on NBC.