The 40-year-old soccer star will appear in his friend's Middle Ages epic opposite Jude Law, Charlie Hunnam, Eric Bana and Poppy Delevingne, reported Huffington Post.
The former England player, however, might appear in a small role as 'Blackleg Leader.'
"There's going to be a version of the scene where Excalibur gets drawn from the stone. This is where Beckham factors in," a source said.
Some 'football puns' were specially written for Beckham's scenes in the film, which began filming this week.
Beckham is also rumoured to be making a cameo appearance in the "Snatch" director's new film "The Man From U.N.C.L.E", scheduled for release in August.