DiCaprio revealed the poster with the brief tweet, "Hollywood".
Once Upon a Time in Hollywood is released in Australia on August 15.
Fans were quick to discuss the new image, with many hinting that the first look shot might have been doctored, and some even suggesting that Brad was photoshopped onto the poster.
Quentin Tarantino's return to the big screen is arriving later this year, in the form of Once Upon a Time in Hollywood, the acclaimed director's take on the infamous Manson Family Murders in 1969.
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Despite the outrage by some, many Tarantino followers shared their excitement for the film when he shared the poster on his Instagram account.
What we do know so far is that the movie will focus on faded TV actor Rick Dalton (DiCaprio) and his stunt double Cliff Booth (Pitt), who want to make a success of themselves in Hollywood's Golden Age.
Once Upon a Time in Hollywood is due to be released into United Kingdom cinemas, meanwhile, on 14 August.
The poster comes as Sony prepares to release the first trailer for Once Upon a Time in Hollywood, which should hit sometime this week.
Once Upon A Time In Hollywood stars an impressive ensemble cast of actors, among them Margot Robbie as Sharon Tate, the actress and wife of filmmaker Roman Polanski who was murdered while pregnant by cult leader Charles Manson and his followers.