Born in Kansas City, Missouri, to Richard and Marie Melvin and raised in New York City by his paternal grandparents, Frank and Helen (née Campbell) Melvin. He attended Columbia University. After graduation, he served in the United States Navy during World War II and married his wife, Amalia Faustina Sestero, in March 1944 in New York City.
While working at a job in the sound effects department of NBC Radio, he did a nightclub act and appeared and won on the Arthur Godfrey’s Talent Scouts radio show. While appearing on Broadway in Stalag 17, he got his break into television by getting the role of Corporal Steve Henshaw on the popular The Phil Silvers Show program. TV fans of this era usually best remember his role as Henshaw, Sergeant Bilko’s right-hand man on that show. “He was proudest of that show,” Amalia Melvin said. “I think the camaraderie of all those guys made it such a pleasant way to work. They were so relaxed.”
During this period, in addition to his role on The Phil Silvers Show, Melvin was often cast in slightly loud, occasionally abrasive, but generally friendly second banana roles. Melvin was also adept at “tough guy” roles; in an example of his range as an actor, one episode of Sergeant Bilko featured Melvin doing a recognizable impersonation of Humphrey Bogart.
In the 1960s, Melvin worked extensively at CBS for Sheldon Leonard and Aaron Ruben. He played Staff Sergeant Charlie Hacker who was Sergeant Vince Carter’s rival for four seasons on Gomer Pyle, USMC. He also made eight appearances on the Dick Van Dyke Show. He also provided the voices of cartoon character Magilla Gorilla, the lion Drooper, on The Banana Splits Adventure Hour, arch villain Tyrone in The Secret Lives of Waldo Kitty and Bluto on The All-New Popeye Hour. Melvin also made eight guest appearances on The Andy Griffith Show in eight different roles, usually as heavies. He also made three guest appearances on Perry Mason in various roles, including reporter Bert Kannon in the 1966 episode, "The Case of the Sausalito Sunrise." Also in 1966 Allan played the space enforcer on the series Lost In Space, in the episode “West Of Mars”.
Melvin is remembered for supporting roles on two popular 1970s sitcoms. He played Sam Franklin, the owner of a local butcher shop and boyfriend of Alice Nelson (the Bradys’ housekeeper) on The Brady Bunch, and Barney Hefner, Archie Bunker’s neighbor and friend on All in the Family. In other contributions to 1970s pop culture, he appeared as a Mel’s Diner patron on Alice and worked as a voice artist (under the name “Al Melvin”). He provided several characters’ voices for the TV show H.R. Pufnstuf and the voice of Prince Thun of the Lion Men on The New Adventures of Flash Gordon.
Some of his most prolific work was in television commercials, for products as diverse as Kellogg's Sugar Frosted Flakes and Remington electric razors. In the latter commercial, he sang a few bars of Frank Loesser’s song “I Believe in You” with a modified lyric. He was also featured as Al the Plumber on Liquid-Plumr drain opener commercials for fifteen years.
In the early 1980s, Melvin appeared as a regular in Archie Bunker’s Place, a successor to All in the Family, in which he played the now more important role of Barney Hefner. When this series ended in 1983, Melvin’s work was exclusively devoted to cartoon voice-overs.
Allan Melvin died of cancer on January 17, 2008, aged 84.