The actress, who plays young musician Ally in the film, posted an emotional statement on social media after hearing the good news, thanking fans for their support.
She wrote: “I can’t believe we just won Best Original Music @BAFTA ‘s . I wish so much I was there but am at the Grammy’s to show them our love as well.
“We made a film about music. This means the world to me. Thank u to all our fans we love u so much, we wouldn’t be here without u #BAFTAs.”
I can’t believe we just won Best Original Music @BAFTA ‘s . I wish so much I was there but am at the Grammy’s to show them our love as well. We made a film about music. This means the world to me. Thank u to all our fans we love u so much, we wouldn’t be here without u #BAFTAs pic.twitter.com/nD8QZgwySB— Lady Gaga (@ladygaga)10 February 2019
The actress is named alongside Bradley Cooper – who directed and starred in the film – and Lukas Nelson for musical score, including for Oscar nominated song Shallow.
A Star Is Born, a remake of the 1937 film, missed out on Best Sound to Bohemian Rhapsody while Cooper lost the Director gong to Roma’s Alfonso Cuarón and Best Actor to Rami Malek, who played Freddie Mercury in the Queen biopic.
And Gaga failed to scoop Best Actress, missing out to Olivia Colman for her critically-acclaimed role in The Favourite.
A Star Is Born is also nominated for a slew of Oscars, with the award ceremony taking place later this month in Los Angeles .
The singer and actress admitted that she “burst into tears” when she slept through the announcement last month.
She told the New York Times: “I’ve been trying to get some sleep because I’m on showbiz time. I woke up around 8:30 and I didn’t know anything about it.”
Gaga then revealed her manager filled in on the details and she “just burst into tears.”
The actress also bagged a nomination for Best Song with Shallow from the same film.
Speaking about the double nomination, Gaga added: “To be recognised as the lead actress and a musician at the same time. I can’t tell you what that means to me.”