The siblings' work on the track earned them the award for Best Original Song.
They also treated the audience to a live performance of 'No Time To Die', with Billie Eilish surrounded by laser-like beams of light moving as she performed the James Bond track.
“This is so unbelievable I could scream", Billie Eilish said, accepting the award. She also paid tribute to the people behind No Time To Die, including rocker Johnny Marr. She said, “Johnny Marr for taking our song and making it worthy of James Bond".
Finneas O'Connell also added, “Lastly we want to thank our parents who have always been our biggest inspirations and heroes. We love you as parents and we love you as real people too. Thank you to the Academy".
Both Billie Eilish and Finneas held off Beyoncé, Lin-Manuel Miranda, Reba McEntire and Van Morrison to the award.
Billie Eilish is now reportedly the youngest artist to win the "triple crown" of film music, having won a Grammy, Golden Globe and now an Oscar for 'No Time To Die'.
