Hefner, who died at the age of 91 on Wednesday, will be buried at Westwood Village Memorial Park in Los Angeles next to Monroe in the same mausoleum, ET has learned.
Hefner famously bought the crypt adjacent to the "Some Like It Hot" star 25 years ago for $75,000.
The Playboy founder will be joining several other huge stars who are buried at the secluded cemetery, including Truman Capote, James Coburn, Rodney Dangerfield, Eva and Zsa Zsa Gabor, Merv Griffin, Dean Martin, Natalie Wood and Farrah Fawcett, to name just a few.
"My father lived an exceptional and impactful life as a media and cultural pioneer and a leading voice behind some of the most significant social and cultural movements of our time in advocating free speech, civil rights and sexual freedom," said Cooper, who currently serves as Chief Creative Officer at Playboy Enterprises.
"He defined a lifestyle and ethos that lie at the heart of the Playboy brand, one of the most recognizable and enduring in history," Cooper added. "He will be greatly missed by many."