Joey Scarbury ( born June 7 , 1955 ) is an adult contemporary singer best known for his hit song , `` Theme from The Greatest American Hero ( Believe It or Not ) '' , in 1981 . Joey Scarbury ( born June 7 , 1955 , in Ontario , California ) is an adult contemporary singer best known for his hit song , `` Theme from The Greatest American Hero ( Believe It or Not ) '' , in 1981 .