Bradley Cooper reunited with Lady Gaga and posed with his daughter at the premiere of 'Maestro.' Here are the 12 best photos.

• Bradley Cooper reunited with his "A Star Is Born" costar Lady Gaga at the LA premiere of "Maestro."
• Cooper also brought his 6-year-old daughter, Lea De Seine, to the event.

Bradley Cooper's new movie "Maestro" premieres on Netflix on December 20.

The film, starring Cooper, Carey Mulligan, and Maya Hawke, is a biopic about the American composer Leonard Bernstein.

Cooper was joined at the Los Angeles premiere on Tuesday night by his 6-year-old daughter, Lea De Seine, and his "A Star Is Born" costar Lady Gaga.

Here are the best photos from the red carpet.

"Maestro" star, writer, and director Bradley Cooper attended the premiere with his 6-year-old daughter, Lea De Seine.

Lea, whose mother is the model Irina Shayk, makes a small cameo in "Maestro."      David Livingston / WireImage

Carey Mulligan plays Felicia Montealegre, Leonard Bernstein's wife.

Bradley Cooper and Carey Mulligan answering questions at Netflix's "Maestro" LA special screening.      Emilio Madrid / Getty Images for Netflix

Lady Gaga, Cooper's costar in "A Star Is Born," also attended the premiere.

"A Star is Born" was Cooper's directorial debut.      Charley Gallay / Getty Images for Netflix

Lady Gaga shared a cute moment with Cooper's daughter.

Lea De Seine and Lady Gaga.      Charley Gallay / Getty Images for Netflix

Cooper also posed with "Maestro" cowriter Josh Singer.

Josh Singer and Bradley Cooper at Netflix's "Maestro" LA special screening.      Mark Von Holden / Variety via Getty Images

Maya Hawke plays Jamie Bernstein, Bernstein's daughter, in the new film.

Maya Hawke is best known for her role in "Stranger Things" and her famous parents, Ethan Hawke and Uma Thurman.      David Livingston / WireImage

Hawke and Mulligan had a humorous moment on the red carpet.

Maya Hawke and Carey Mulligan at Netflix's "Maestro" LA special screening.      Tommaso Boddi / Getty Images

Matt Bomer, who stars as David Oppenheim, posed on the red carpet with his "Fellow Travelers" costar Jonathan Bailey.

The pair play lovers in the new TV series "Fellow Travelers."      David Livingston / WireImage

Legendary director Steven Spielberg attended the premiere.

Steven Spielberg is a producer on "Maestro."      Emilio Madrid / Getty Images for Netflix

Ed Helms, who starred in the "Hangover" movies with Cooper, walked the carpet.

Ed Helms played Stu in the franchise.      David Livingston / WireImage

Leonard Bernstein's three children, Nina, Alexander, and Jamie, also attended the event.

Nina Bernstein, Alexander Bernstein, and Jamie Bernstein at Netflix's "Maestro" LA special screening.      David Livingston / WireImage