Family spokesman Eddy Friedfeld said Caesar, who also played Coach Calhoun in the 1978 movie "Grease," died at his home in the Los Angeles area after a brief illness.
"He had not been well for a while. He was getting weak," said Friedfeld, who lives in New York and last spoke to Caesar about 10 days ago.
Friedfeld, who with Caesar wrote the 2003 biography "Caesar's Hours: My Life in Comedy, With Love and Laughter," learned of his friend's death in an early morning call from Caesar's daughter, Karen.
In his two most important series, "Your Show of Shows," 1950-54, and "Caesar's Hour," 1954-57, Caesar displayed remarkable skill in pantomime, satire, mimicry, dialect and sketch comedy. And he gathered a stable of young writers who went on to worldwide fame in their own right - including Carl Reiner, Neil Simon, Larry Gelbart ("M-A-S-H"), and Allen.
"He was one of the truly great comedians of my time and one of the finest privileges I've had in my entire career was that I was able to work for him," Allen said in a statement.
Reiner, who was a writer-performer on the breakthrough "Your Show of Shows" sketch program, told KNX-AM Los Angeles that he had an ability to "connect with an audience and make them roar with laughter."
In a statement, Reiner called Caesar "inarguably the greatest pantomimist, monologist and single sketch comedian who ever worked in television," adding that the actor-comedian was a great flame who attracted "all the comedy moths" including Brooks and Simon.
Friedfeld said Caesar always shared the acclaim.
"Sid was an innovator, he and his team. He was very careful about never taking credit alone. He believed in his co-stars and his writers," he said. "They created the amazing vehicles for him to be creative."
While best known for his TV shows, which have been revived on DVD in recent years, Caesar also had success on Broadway and occasional film appearances, notably in "It's a Mad Mad Mad Mad World."
If the typical funnyman was tubby or short and scrawny, Caesar was tall and powerful, with a clown's loose limbs and rubbery face, and a trademark mole on his left cheek.
But Caesar never went in for clowning or jokes. He wasn't interested. He insisted that the laughs come from the everyday.
"Real life is the true comedy," he said in a 2001 interview with The Associated Press. "Then everybody knows what you're talking about." Caesar brought observational comedy to TV before the term, or such latter-day practitioners as Jerry Seinfeld, were even born.
The son of Jewish immigrants, Caesar was a wizard at spouting melting-pot gibberish that parodied German, Russian, French and other languages.
Some compared him to Charlie Chaplin for his success at combining humor with touches of pathos.
Caesar performed with such talents as Howard Morris and Nanette Fabray, but his most celebrated collaborator was the brilliant Imogene Coca, his "Your Show of Shows" co-star.
Reiner went on to base his "Dick Van Dyke Show" - with its fictional TV writers and their temperamental star - on his experiences there. Simon's 1993 "Laughter on the 23rd Floor" and the 1982 movie "My Favorite Year" also were based on the Caesar show.
Increasing ratings competition from Lawrence Welk's variety show put "Caesar's Hour" off the air in 1957.
In 1962, Caesar starred on Broadway in the musical "Little Me," written by Simon, and was nominated for a Tony. He played seven different roles, from a comically perfect young man to a tyrannical movie director to a prince of an impoverished European kingdom.
In 1976, he put his pantomime skills to work in Brooks' "Silent Movie."
But he later looked back on those years as painful ones. He said he beat a severe, decades-long barbiturate and alcohol habit in 1978, when he was so low he considered suicide. "I had to come to terms with myself. 'Yes or no? Do you want to live or die?'" Deciding he wanted to live, he recalled, was the "first step on a long journey."
Caesar was born in 1922 in Yonkers, N.Y., the third son of an Austrian-born restaurant owner and his Russian-born wife. His first dream was to become a musician, and he played saxophone in bands in his teens.
But as a youngster waiting tables at his father's luncheonette, he liked to observe as well as serve the diverse clientele, and recognize the humor happening before his eyes.
His talent for comedy was discovered when he was serving in the Coast Guard during World War II and got a part in a Coast Guard musical, "Tars and Spars." He also appeared in the movie version. Wrote famed columnist Hedda Hopper: "I hear the picture's good, with Sid Caesar a four-way threat. He writes, sings, dances and makes with the comedy."
That led to a few other film roles, nightclub engagements, and then his breakthrough hit, a 1948 Broadway revue called "Make Mine Manhattan."
His first TV comedy-variety show, "The Admiral Broadway Revue," premiered in February 1949. But it was off the air by June. Its fatal shortcoming: unimagined popularity. It was selling more Admiral television sets than the company could make, and Admiral, its exclusive sponsor, pulled out.
But everyone was ready for Caesar's subsequent efforts. "Your Show of Shows," which debuted in February 1950, and "Caesar's Hour" three years later reached as many as 60 million viewers weekly and earned its star $1 million annually at a time when $5, he later noted, bought a steak dinner for two.
When "Caesar's Hour" left the air in 1957, Caesar was only 34. But the unforgiving cycle of weekly television had taken a toll: He had started relying on booze and pills for sleep every night so he could wake up and create more comedy.
It took decades for Caesar to hit bottom. In 1977, he was onstage in Regina, Canada, doing Simon's "The Last of the Red Hot Lovers" when, suddenly, his mind went blank. He walked off stage, checked into a hospital and went cold turkey. Recovery had begun, with the help of wife Florence Caesar, who would be by his side for more than 60 years and helped him weather his demons.
Florence Caesar died four years ago, Friedfeld said.
Those demons included remorse about the flared-out superstardom of his youth - and how the pressures nearly killed him. But over time he learned to view his life philosophically.
"You think just because something good happens, THEN something bad has got to happen? Not necessarily," he said with a smile in 2003, pleased to share his hard-won wisdom: "Two good things have happened in a row."
Funeral services were pending.