Greta Gerwig's deep but funny feminist parody of the famous doll starring Margot Robbie opened in competition with Christopher Nolan's new biopic starring Cillian Murphy as physicist J Robert Oppenheimer who helped develop the first nuclear weapons.
Barbie took the top spot, making $100m (£77.9m) at the US domestic box office over the weekend, but Oppenheimer still made $50m (£38.9m) - making history as the first time a film has taken $50m in ticket sales at the same time as a movie made over $100m.
Figures for the UK box office are yet to be published. But Vue cinema chain, which has 91 theatres throughout the UK and Ireland, said it had its highest grossing weekend since Avengers Endgame in 2019 - before the coronavirus pandemic forced cinemas to close their doors.
Odeon cinemas reported that more than 10,000 advanced tickets had been purchased to see both films in their opening weekend.
Barbie made £141.9m in ticket sales at box offices outside the US and Oppenheimer took £73m in comparison.
This meant the total global sales for both films were £398m worldwide, with Barbie making £262.5m and Oppenheimer achieving £135.5.
Oppenheimer was released in 79 territories, while higher-grossing Barbie only opened in 70, with several countries choosing to ban the 12A film.
Vietnam has banned the Barbie movie over a controversial map of the South China Sea included in the film, while Pakistan has imposed a temporary ban due to the movie's LGBTQ+ themes.
Read more: Is Barbie suitable for kids?
Gerwig's Barbie now holds the record for the highest grossing opening weekend for a film directed by a woman, as well as studio Warner Bros' largest advance sales ever at £38.5m.
For director Nolan Oppenheimer is only his third biggest box office taking, behind Batman movies The Dark Knight and Dark Knight Rises. But it is now his highest grossing opening weekend in IMAX screenings.
The new biopic has achieved the best opening weekend for a drama since 2019, overtaking Creed III, and the highest grossing opening for an R-rated film, knocking John Wick Chapter 4 from the top spot.
Watch: Barbenheimer is a box office success all round