Martin was born and raised in the small town of Mars Hill, North Carolina, in the state's western mountains. His father was an ordained Baptist minister. He graduated from Wake Forest College in 1932. During World War II, he was a U.S. Army Intelligence Officer, and was aboard the USS Missouri for the Japanese Surrender in 1945.
Martin first worked in the diplomatic field at the U.S. Embassy in Paris, France, from 1947 to 1955. His abilities as an administrative counselor and deputy Chief of Mission gained him attention from the State Department, which rapidly advanced his career. President Eisenhower appointed Martin as the Representative of the United States to the European Office of the United Nations in Geneva, and he served in that office 1960–62.
Martin was appointed on 10 September 1963 and left this post on 9 September 1967.
While serving as ambassador to Thailand, Martin came to the attention of Richard Nixon during a state banquet for the Thai King. Nixon was with Vice-President Hubert Humphrey. When the King toasted President Johnson, Humphrey tried to return the toast with a toast to the King. Martin interceded and gave the toast himself, explaining later to both Humphrey and Nixon that as the Ambassador, he was the President's personal representative, and thus, outranked the Vice President. He finished his explanation by saying "If you become President yourself someday, Mr. Vice President, you can be sure that I will guard your interests as closely as I did President Johnson's tonight".
Martin was appointed on 30 October 1969 and left this post on 10 February 1973.
Martin was appointed as Ambassador to South Vietnam on 21 June 1973. (In 1965 his foster son died in combat in Vietnam.)
The ambassador seriously underestimated the severity of the South Vietnamese situation, to the point that in the spring of 1975, when most American officials were convinced that South Vietnam was doomed to collapse, he continued to believe that Saigon and the Mekong Delta area could be held because of the tenacity of the Army of the Republic of Vietnam (ARVN) in the Battle of Xuan Loc under the command of General Le Minh Dao.
In fact, in the NSA history The Secret Sentry, the author says: "In Saigon, Ambassador Graham Martin refused to believe the SIGINT (signals intelligence) reporting that detailed the massive North Vietnamese military buildup taking place all around (Saigon) ... and repeatedly refused to allow NSA's station chief, Tom Glenn, to evacuate his forty-three man staff and their twenty-two dependents from Saigon." Because of Martin's refusal to believe the SIGINT, and his refusal to allow the evacuation of the intelligence staff from the embassy, "(t)he North Vietnamese captured the entire twenty-seven-hundred-man (South Vietnamese SIGINT) organization inact [sic] as well as their equipment." (ibid)
Martin was evacuated by helicopter from the US Embassy, Saigon on the morning of 30 April 1975 as Communist forces overran the city. Though he didn't know it, the helicopters crew had orders to arrest him and bring him on board by force if he'd refused to go. (The helicopter used was a USMC CH-46 Sea Knight call sign Lady Ace 09 of HMM-165 serial number 154803. Ambassador Martin's wife, Dorothy, had already been evacuated by previous flights, and left behind her personal suitcase so a South Vietnamese woman might be able to squeeze on board with her.)
Martin died in March 1990 and is buried in Section 3 at Arlington National Cemetery.
While Martin was serving as Ambassador to Thailand, his foster son, Marine 1stLt Glenn Dill Mann, was killed near Chu Lai, South Vietnam, in November 1965, while attacking enemy positions at Thach Tru with his UH-1 helicopter gunship. 1stLt Mann is buried in Section 3 at Arlington National Cemetery.
The helicopter that evacuated the ambassador out of Saigon, on the same day the Vietnam War ended, is on display at the Flying Leatherneck Aviation Museum in San Diego, California.