A 1942 graduate of Phillips Academy, Coffin has led a varied and accomplished career often taking controversial stands on civil rights and peace issues. Coffin served as a World War II infantry officer and liaison to the French and Russian armies and later served as a CIA operative, training anti-Soviet Russians for operation within the Soviet Union. He graduated from Yale University in 1949 and later entered Yale Divinity School and received a bachelor of divinity degree in 1956. He was chaplain of Yale University (1957-1975), senior minister of the Riverside Church in New York City (1977-1987), and president of the nuclear disarmament advocacy group SANE FREEZE (1987-1990).
Coffin gained national prominence in the early 1960s as a Freedom Rider, one of a group of activists, black and white, who rode interstate buses in the South to protest segregation laws. He was arrested, but the conviction was later overturned by the U.S. Supreme Court. During the Vietnam War, he gained national attention after his arrest (along with Dr. Benjamin Spock, graduate of the Phillips Academy Class of 1921), on charges of conspiracy to aid military draft resisters. The charges were dropped on appeal.