The producer passed away unexpectedly in his home near Coeur d'Alene, Idaho, on Monday. The cause of death has not been specified.
Sellier is best known for creating the character Grizzly Adams, a man accused of murder who befriends a bear while on the run from bounty hunters.
Adams, who was inspired by an actual 19th century trapper, was played by actor Dan Haggerty in the 1974 film The Life and Times of Grizzly Adams and the subsequent TV series of the same name.
Sellier also wrote and produced religious-based TV movies and documentaries, including In Search of Noah's Ark and Mark Twain's America.
He received an Emmy nomination in 1980 for TV movie The Legend of Sleepy Hollow.