For comparison, here's what the real Sharon Tate looked like.
Quentin Tarantino is helming the period project, which will center around the Manson family murders. The "Valley of the Dolls" actress was married to Roman Polanski at the time, and was heavily pregnant with their son.
In a statement the Kill Bill filmmaker said: "I couldn't be happier about the dynamic teaming of DiCaprio & Pitt as Rick & Cliff".
The next night, Manson Family members entered the home of grocer Leno LaBianca and his wife Rosemary LaBianca, and murdered them too.
Once Upon a Time in Hollywood is based on the brutal murder of Sharon Tate by followers of Charles Manson in 1969 inside her Cielo Drive home in Hollywood. His sidekick Cliff Booth (Pitt) - who's also his stunt double - is looking for the same thing.
Set in Los Angeles in the summer of 1969, Once Upon a Time in Hollywood focuses on a male TV actor named Rick Dalton (DiCaprio) who's had one hit western series and is looking for a way to get into the film business.
"#Tarantino movie people think they know what this movie is, they don't I'm grateful to Quentin for letting me read the script, and sitting down with me to explain his vision", she wrote, adding, "I have to protect my sisters legacy and to do what I can to make sure her memory is not exploited".
In perhaps an act of good faith, Sony also moved up the released date of the film to July 26, 2019 - two weeks before it was originally set to be released on August 9, 2019, the 50th anniversary of Tate's murder.