His manager and producing partner Daniel Ostroff has confirmed. He was 69.
According to Ostroff, Blake died peacefully in Tucson, Ariz, after battling a long illness.
Blake wrote the novel "Dances With Wolves" in 1988, before it was turned into an Oscar-winning feature. The book would go on to sell more than 3.5 million copies and be translated into 15 different languages.
The film came out in 1990, directed by and starring Kevin Costner, and was both a commercial and critical smash.
Along with screenplay, it won six other Oscars, including best picture. The script also won the prize at the WGA Awards and the Golden Globes.
Blake most recently wrote a screenplay based on German novel "Winnetou" for Constantin Films in 2011.