Hollywood star Pitt will play the fictional character Sonny Hayes, and Hamilton has been brought on board to, in his own words, 'try to call BS' where needed.
Hamilton has won a joint-record seven F1 world titles, and there are few better placed to give the Hollywood A-lister tips - or so you might think!
The pair were in Los Angeles recently and Hamilton, who has been telling Pitt about racing nuances like "the braking point to the turning point to the apex", nearly failed to take his own advice.
"We were in L.A. and we went to this track and I showed him around and nearly put the car in a wall actually!" Hamilton admitted in a YouTube Q&A with GQ Sports. "I was just on the edge - wasn't really near - but a hair-raising moment!
"He's got a real knack for it already so he's just been working on honing that skill but every now and then you're just like 'oh that's Brad!'"
Hamilton has a reputation as a clean driver but has had 31 DNFs in his career. He completed every race in 2017, 2019 and 2022, however.
Kosinski's film began production at Silverstone last July during the British Grand Prix weekend, with Pitt driving a modified Formula Two car.
ESPN reported that the film was titled 'Apex', but it later retracted this statement.
It will be the second F1 film in quick succession following last August's Enzo Ferrari biopic - simply titled 'Ferrari' - in which Adam Driver played the lead.
The film has grossed $43 million worldwide and received generally positive reviews from critics.