A native of Providence, Rhode Island, MacDermott graduated in 1960 from Trinity College in Hartford, Connecticut. He began his coaching career in 1961 at Hopkins School in New Haven, Connecticut. He spent six years as the football and wrestling coach at the Hopkins School. From 1966 to 1970, he was an assistant football coach at Wesleyan University in Middletown, Connecticut. He was named Wesleyan's head football coach in December 1970 following the retirement of Don Russell. He continued to hold that position through the 1986 season. In 16 years as the head coach at Wesleyan, MacDermott compiled a record of 66–59–3. His 66 wins rank him third among all head coaches in the history of the Wesleyan football program. During his tenure at Wesleyan, MacDermott coached Bill Belichick, who would himself go on to have a distinguished coaching career in the NFL. MacDermott also served as the wrestling coach at Wesleyan.