Nelson was born Robert Haakon Nielsen in San Francisco, California, of Norwegian ancestry, the son of Betsy (née Christophsen) and Trygve Nielsen. (His year of birth has been reported variously, but his 1943 Army enlistment record and his 1993 voter registration records certify 1917 as the correct year of his birth.) He began acting in school at the age of fifteen. He graduated from the University of California, Berkeley in 1941 and, because of his theatrical efforts in school, was almost immediately signed to amotion picture contract by Metro-Goldwyn-Mayer Studios.
Barry Nelson played as Ian Flemings James Bond in Casino Royale he was the first to play James Bond. As an MGM contract player, Nelson made his screen debut in the role as Paul Clark in Shadow of the Thin Man (1941) starring William Powell and Myrna Loy, withDonna Reed. He followed that with his role as Lew Rankin in the film noir crime/drama Johnny Eager (1942) starring Robert Taylorand Lana Turner.He played the lead in an MGM second feature war film A Yank on the Burma Road. (1942)
During his military service in World War II, Nelson debuted on the Broadway stage in one of the leading roles, Bobby Grills, in Moss Hart's play Winged Victory (1943). His next Broadway appearance was as Peter Sloan in Hart's Light Up the Sky (1948), which was a first-rate success. He went on to appear on Broadway with Barbara Bel Geddes in the original Broadway production of The Moon is Blue; he was the last surviving original cast member of the production. During the play's run he also starred in a CBS half-hour drama called The Hunter, premiering in July 1952. He played Bart Adams, a wealthy young American whose business activities involved him in a series of adventures. He also appeared opposite Lauren Bacall in the Abe Burrows comedy Cactus Flower in 1965 and withDorothy Loudon in The Fig Leaves Are Falling in 1969. Another Broadway role, that of Gus Hammer in The Rat Race (1949), kept Nelson away from the movies again, but after it closed he starred in the dual roles as Chick Graham and Bert Rand in The Man with My Face (1951), which was produced by Ed Gardner of radio fame.
He was the first actor (and the first non European before George Lazenby who was the second) to play James Bond on screen, in a 1954 adaptation of Ian Fleming's novel Casino Royale on the television anthology series Climax! (preceding Sean Connery's interpretation in Dr. No by eight years). Reportedly this was considered a pilot for a possible James Bond television series, though it's not known if Nelson intended to continue playing the character. Nelson played James Bond as an American named "Jimmy Bond".
The program also featured Peter Lorre as the primary villain, Le Chiffre; Nelson later noted Lorre was the reason he took the role. Originally broadcast live, the production was believed lost until a kinescope emerged in the 1980s. It was subsequently released to home video, and is currently available on DVD as a bonus feature with the 1967 film adaptation of the novel.
Nelson appeared as Grant Decker in "Threat of Evil", a 1960 episode of CBS's anthology series The DuPont Show with June Allyson. His additional television credits include guest appearances on Alfred Hitchcock Presents, Ben Casey, The Twilight Zone (episode "Stopover In A Quiet Town"), and Dr. Kildare. He appeared regularly on television in the 1960s, having been one of the What's My Line? mystery guests and later serving as a guest panelist on that popular CBS quiz show. Nelson appeared in both the stage and screen versions of Mary, Mary. In 1978, he was nominated for a Tony Award for Best Actor in a Musical for his role as Dan Connors in The Act (1977) with Liza Minnelli. His final appearance on Broadway was as Julian Marsh in 42nd Street (1986). William Goldman, in his 1968 book The Season, called Nelson a consummately professional actor.
"He was a very naturalistic, believable actor," said his agent, Francis Delduca. "He was good at both comedy and the serious stuff."
Among his other film credits were Airport and The Shining (as the hotel manager who interviews Jack Nicholson for a job opening), and he also appeared on such television series as Murder, She Wrote, Dallas and Magnum, P.I. More recently, Nelson and his second wife spent a lot of time travelling. He planned to write a couple of books about his time on stage and in Hollywood.
From 1964 to 1966, he hosted portions of the NBC Radio program Monitor.
Nelson had two wives, actress Teresa Celli, married in 1951 and later divorced, and Nansilee ("Nansi") Hoy, to whom he was married until his death. Nelson and his second wife divided their time between homes in New York and France. Until his death, Nelson could be seen publicly at American Civil War shows across America. He was a close friend of tenor Mario Lanza.
According to his widow Nansi, Barry Nelson died on April 7, 2007, while traveling in Bucks County, Pennsylvania, nine days before his 90th birthday. The cause of death was not disclosed.