Denver graduated from Loyola-Marymount University in Los Angeles, California, USA and worked as a mailman and a high school teacher before landing the role of Maynard G. Krebs on "The Many Loves of Dobie Gillis" in 1959. His costar Dwayne Hickman, who played Dobie Gillis, was also a graduate of Loyola-Marymount University. After the show ended in 1963, Denver landed the role of Gilligan on "Gilligan's Island". After the show ended in 1967, Denver appeared in other television shows including, "The Good Guys" (1968-1974) and "Dusty's Trail" (1973), however none matched the success of his earlier roles.