The poster, released on Monday, feature the pair posing together in front of a yellow car and California's Hollywood sign.
DiCaprio and Pitt are wearing 1960s clothing as the film is set during the Manson Family murders which took place in 1969. DiCaprio is set to portray fictional fading television star Rick Dalton with Pitt as his stunt double Cliff Booth.
Dakota Fanning stars as Manson Family associate Lynette 'Squeaky' Fromme and Damian Lewis stars as actor Steve McQueen. Al Pacino, Emile Hirsch, Timothy Olyphant, James Marsden and Tim Roth are also set to star.
Once Upon a Time in Hollywood, the ninth film from Tarantino, is set to arrive in theaters on July 26.