Coffin made his screen debut in 1973 when he appeared in the television film Much Ado About Nothing, an adaptation of the play, in which he also starred.

In 1999, Coffin would appear, in perhaps his best known role among millennials, as corrupt business man Parker Wyndham in the Disney Channel original movie Zenon: Girl of the 21st Century.

He also made guest appearances in many well known series including Kojak, Hill Street Blues, Moonlighting, The Twilight Zone, Remington Steele, Dallas, in which he appeared for six episodes, L.A. Law, The X-Files, Walker, Texas Ranger, Murder, She Wrote, Dr. Quinn, Medicine Woman, and the soap operas Ryan's Hope and The Edge of Night.

In 1997, he returned to his alma mater as that year's Knight Fellow, one of Western Reserve Academy's most distinguished honors.

[1] Coffin was married to actress Barbara Monte-Britton from September 25, 1977, to his death on July 31, 2003, from lung cancer; he was a long-time chain smoker.