The fling happened during the filming of 1959 hit comedy Some Like It Hot in which the pair starred together. However, the Kansa Raiders star says that they first had an affair in 1950, which ignited once again in September 1958.
He has disclosed in the book, which is set to publish in September in the US, that the affair ended when the shooting for the movie got over. Their relationship apparently developed while Monroe was married to playwright Arthur Miller and Curtis was hitched to Psycho star Janet Leigh, who was expecting their second daughter Jamie Lee Curtis.
In his book, Curtis claims Monroe told him in October that she was pregnant with his child during an argument between the pair and Miller. And in December the same year, he came to know that she had miscarried. The 84-year-old actor says that Marilyn was a mysterious figure in real life and he could never forget the time he spent with her.
"When I was in bed with Marilyn, I was never sure, before, during or after, where her mind was," the Daily Express quoted him as stating. He added: "She was an actress. She could play a part. She could give the part what she thought a man wanted. I never asked for more. What I experienced with her was unforgettable."
The star has lived a trouble life, marked by cocaine addiction and depression, losing a son to heroin and more recently ending up in coma after a bout of pneumonia. Monroe died in 1962 at the age of 36.