On June 15, 2014, Kasem died in St. Anthony's Hospital in Gig Harbor, Washington of Lewy body dementia at age 82.
He was married to Linda Myers, to which they had 3 children. Until his death in 2014, he was then married to Jean Kasem and they had 1 child.
He was a vegetarian.
Kasem was best known for his distinctive voice acting, doing the voice of Shaggy in the various Scooby-Doo programs and various characters in Transformers. He was also credited with additional voice roles in The Super Powers Team: Galactic Guardians, Super Friends: The Legendary Super Powers Show, Super Friends, Challenge of the Super Friends, Battle of the Planets, and Josie and the Pussycats.
He also made several appearances on television, in which he played himself.
Having worked in radio since the early 1960s, Kasem founded the American Top 40 in 1970 and hosted it until 1988 and then again from 1998 to 2004. He also hosted America's Top 10 for a time and Casey's Top 40.