Stang once claimed he got his break in radio by sending a postcard to a New York station requesting an audition, was accepted, and then bought his own ticket to New York from Chelsea, Massachusetts with the money set aside for his mother's anniversary gift.. True or not, Stang worked on New York-based network radio shows as a boy, appearing on children's programs such as The Horn and Hardart Hour and Let's Pretend.. By 1940, he had graduated to teenaged roles, appearing on The Goldbergs. Director Don Bernard hired him in October 1941 to do the commercials on the CBS program Meet Mr. Meek but decided his voice cracking between soprano and bass would hurt the commercial so he ordered scriptwriters to come up with a role for him.. He next appeared on the summer replacement show The Remarkable Miss Tuttle with Edna May Oliver in 1942 and replaced Eddie Firestone Jr. in the title role of That Brewster Boy when Firestone joined the U.S. Marine Corps in 1943.

Comedian Henry Morgan made him a sidekick on his program in fall of 1946 and Stang appeared in similar roles the following year on radio shows with Eddie Cantor and Milton Berle.

At this time Stang had appeared in a number of movies, including Seven Days Leave, My Sister Eileen and They Got Me Covered. He had also appeared on the Broadway stage in Sailor Beware, All In Favor and Same Time Next Week where he first worked with Berle.

Stang moved to television at the start of the Golden Age. He had a recurring role in the TV show The School House on the DuMont Television Network in 1949. He was a regular on Eddie Mayehoff's short-lived situation comedy Doc Corkle in fall of 1952. Then he made a guest appearance on Milton Berle's Texaco Star Theater on May 12, 1953 and joined him as a regular the following September, often berating or heckling the big-egoed star for big laughs. Stang also had guest roles on several variety shows of the day including The Colgate Comedy Hour.

In films, he played Sparrow in The Man with the Golden Arm (1955) with Frank Sinatra and Kim Novak. In It's a Mad, Mad, Mad, Mad World (1963) he played Ray, who along with his partner Irwin (played by Marvin Kaplan), owns a gas station that Jonathan Winters destroys for defending Otto Meyer (Phil Silvers). He appeared in Hello Down There (1969). In one of the oddest movie pairings, he partnered with Arnold Schwarzenegger (billed as "Arnold Strong") in the latter's first film, the camp classic Hercules in New York (1970).

Stang was often a voice actor for animated cartoons. He provided the voice for Popeye's pal Shorty (a caricature of Stang), Herman the mouse in a number of Famous Studios cartoons, Tubby Tompkins in a few Little Lulu shorts, the famous Hanna-Barbera lead character Top Cat (modeled explicitly on Silvers' Sgt. Bilko), and Catfish on Misterjaw. He also provided many extra voices for the Cartoon Network series Courage the Cowardly Dog.

On television he appeared in commercials for the Chunky candy bar, where he would list many of its ingredients, smile and say, "Chunky, what a chunk of chocolate!" He provided the voice of the Honey Nut Cheerios Bee in the 1980s and was also a spokesman for Vicks Vapo-Rub. As a pitchman for Alcoa aluminum window screens in the late 1960's, he was known for the tag line "Arnold Stang says don't get stung".

Stang once described himself as "a frightened chipmunk who's been out in the rain too long." As for his squawky, Brooklyn voice, he said "I'm kind of attached to it...[it's] a personal logo. It's like you're Jell-O or Xerox.

Stang appeared on an episode of The Cosby Show with guest star Sammy Davis Jr. In one TV ad he played Luther Burbank, proudly showing off his newly-invented "square tomato" to fit neatly in typical square slices of commercial bread, then being informed that the advertising bakery had beat him to it by producing round loaves of bread. He played the photographer in the 1993 film Dennis the Menace with Walter Matthau.

Stang died of pneumonia in Newton, Massachusetts, on December 20, 2009. Stang was born in New York City in 1918, but often claimed Chelsea, Massachusetts as his birthplace and 1925 as his birthdate.