Del Monroe was born in Santa Barbara. After finishing school Monroe joined the army and it was then when he first became interested in acting. He enrolled in the Pasadena Playhouse where he appeared in more than 30 plays. In 1961 Irwin Allen asked Monroe to play the character of Seaman Kowski in the film Voyage to the Bottom of the Sea. He later played Seaman Kowalski in the television show of the same name. After "Voyage" ended Monroe made a guest star appearance in another Irwin Allen show, The Time Tunnel, playing the part of Ott in "The Kidnappers" episode and also appeared in many other television shows including 'Gunsmoke', 'Emergency!', 'Mannix', 'Wonder Woman', 'Dukes of Hazzard', 'The Incredible Hulk', 'Hunter', 'The Fall Guy', and 'Fame'. Most recently Del was nominated for a best actor award on stage.
His final appearance was in an episode of "Medium" in 2005.
Del passed away on June 5, 2009.