Benny began studying the violin, an instrument that would become his trademark, when he was six. By fourteen he was playing in local dance bands, as well as in his high school orchestra, until he failed school and left for a career in vaudeville. In 1911, he was playing in the same theater as the young Marx Brothers, whose mother was so enchanted with Benny that she invited him to be their permanent accompanist. The plan was foiled by Benny's parents, who refused to let their son, then seventeen, go on the road, but it was the beginning of his long friendship with Zeppo Marx.
The following year, Benny formed a vaudeville musical duo with pianist Cora Salisbury. This provoked famous violinist Jan Kubelik, who thought that the young vaudeville entertainer with a similar name (Kubelsky) would damage his reputation. Finally, Bejamin Kubelsky agreed to change his name to Ben K. Benny (sometimes spelled Bennie). He also found a new pianist, Lyman Wood. He left show business briefly in 1917 to join the Navy during World War I, but even then, he often entertained the troops. One evening, he was booed by the troops, so he began telling Navy jokes on stage. He was a big hit, earning himself a reputation as a comedian as well as a musician.
After the war, Benny returned to vaudeville and changed his first name to Jack. He had several romantic encounters, including with a dancer, Mary Kelly, whose devoutly Catholic family forced her to turn down Benny's proposal because he was Jewish. In 1922, he accompanied Zeppo Marx to a Passover seder in Vancouver, where he met Sadie Marks, whom he eventually married in 1927. As Mary Livingstone, she was his collaborator throughout his career.
A major vaudeville star, Benny also began making movies, including the Academy Award-winning The Hollywood Revue of 1929 and notably, Charley's Aunt (1941) and To Be or Not to Be (1942). He also had an enormously successful radio career with his The Jack Benny Program, which ran from 1932 to 1955. It was on this show, in 1937, that he began his feud with rival comedian Fred Allen, who complained about the way Benny played violin. In fact, the two of them were really close friends. A typical Benny and Allen episode, in this case on Fred's radio show, was a satire of "Queen for a Day" re-titled "King for a Day". In it, Allen plays host and eventually showers Benny with a ton of worthless prizes in honor of him being named King for a Day. The grand prize is a pants pressing from a local dry cleaning company. The hilarity builds as Jack's shirt is being taken off. Then, his pants are pulled off to the shock of the audience. The laughter was so loud and chaotic at the chain of events that Fred's announcer, Kenny Delmar, was cut off the air amidst the wild laughter while trying to read the credits...Fred's show had ran over-time yet again! Another of his friends and frequent guest-stars was George Burns of Burns and Allen. Benny's show also starred his wife Mary Livingstone, Eddie "Rochester" Anderson, Phil Harris, Dennis Day, announcer Don Wilson, Frank Nelson, and the remarkably versatile Mel Blanc. Ronald Colman and his wife Benita appeared frequently in the 1940s as Benny's neighbors.
During his early radio show, Benny adopted "Love in Bloom" as his theme song, opening every show. The song later became the theme of his television show too. His shows featured a fictionalized version of Benny's life with many running gags, particularly jokes about Benny's cheapness. One of the most famous silences in radio came when Benny was accosted by a robber who demanded, "Your money or your life!" After an extended pause, Benny replied, "I'm thinking it over."
The Jack Benny Show ran on television from October 28, 1950 to 1965). Actually, during his first two years on TV, he appeared infrequently then the next two years every fourth week. From 1955-1960 he appeared every other week and from 1960-1965 he was seen weekly. When Benny moved to television, he revealed that his verbal talent was matched by his assortment of facial expressions.
Jack's sponsors were many: Canada Dry Ginger Ale: 1932-1933; Chevrolet: 1933-1934; General Tire: 1934; Jell-O from 1934-1942; Grape Nuts Flakes from 1942-1944; and finally Lucky Strike from 1944-1955. The commercials were incorporated into the body of the show; the sponsors were often the butt of jokes.
The program's plots centered around putting on a radio program and were set partly in the studio and partly in Benny's home. Rochester ran the house. Jack was single on the show. His real-life wife, Mary Livingstone, was presented as Jack's leading lady on the radio show. Mary had many running jokes of her own, including her romantic interest in many of the guests, and her former employment as salesgirl at the May Department Stores, where Jack had supposedly met Mary, in the lingerie department.
The show-within-a-show setting was an example of breaking the fourth wall by bringing the audience in on the joke that it was "just a show".
Toward the end of his career, Benny returned to film, appearing most notably in It's a Mad, Mad World in (1963). He was cast in Neil Simon's The Sunshine Boys, but he was forced to give up the role, when he was diagnosed with terminal pancreatic cancer. He died in 1974. He was interred in the Hillside Memorial Park Cemetery in Culver City, California.
Today, Benny is thought of as the premier comedian of old-time radio.