Berle appeared as a child actor in silent films, beginning with The Perils of Pauline (1914), filmed in Fort Lee, New Jersey, with Pearl White.
The director told Berle that he would portray a little boy who would be thrown from a moving train. In Milton Berle: An Autobiography (1975), he explained, "I was scared shitless, even when he went on to tell me that Pauline would save my life. Which is exactly what happened, except that at the crucial moment they threw a bundle of rags instead of me from the train. I bet there are a lot of comedians around today who are sorry about that."
By Berle's account, he continued to play child roles in other films: Bunny's Little Brother (1914) with John Bunny; Tess of the Storm Country (1914) with Mary Pickford; Birthright (1920) with Flora Finch; Love's Penalty (1921) with Hope Hampton; Divorce Coupons (1922) with Corinne Griffith and the serial Ruth of the Range (1923) with Ruth Roland. Berle recalled, "There were even trips out to Hollywood — the studios paid — where I got parts in Rebecca of Sunnybrook Farm, with Mary Pickford; The Mark of Zorro, with Douglas Fairbanks, Sr., and Tillie's Punctured Romance, with Charlie Chaplin, Mabel Normand and Marie Dressler."
However, Berle's claims to have appeared in many of these films, particularly the 1914 Chaplin Keystone comedy Tillie's Punctured Romance, are hotly disputed by some, who cite the lack of supporting evidence that Berle even visited the West Coast until much later. The newsboy role often claimed by Berle in "Tillie" was unquestionably played by resident Keystone child actor Gordon Griffith.
In 1916, Berle enrolled in the Professional Children's School, and at age 12 he made his stage debut in Florodora. After four weeks in Atlantic City, New Jersey, the show moved to Broadway. It catapulted him into a comedic career that spanned eight decades in nightclubs, Broadway shows, vaudeville, Las Vegas, films, television and radio.
Berle continued to dabble in songwriting. With Ben Oakland and Milton Drake, Berle wrote the title song for the RKO Radio Pictures release Li'l Abner (1940), an adaptation of Al Capp's comic strip, featuring Buster Keaton as Lonesome Polecat. Berle wrote a Spike Jones B-side, "Leave the Dishes in the Sink, Ma."
Three Ring Time, a comedy-variety show sponsored by Ballantine Ale, was followed by a 1943 program sponsored by Campbell's Soups. The audience participation show Let Yourself Go (1944–45) could best be described as slapstick radio with studio audience members acting out long suppressed urges (often directed at host Berle). Kiss and Make Up, on CBS in 1946, featured the problems of contestants decided by a jury from the studio audience with Berle as the judge. He also made guest appearances on many comedy-variety radio programs during the 1930s and 1940s.
Scripted by Hal Block and Martin Ragaway, The Milton Berle Show brought Berle together with Arnold Stang, later a familiar face as Berle's TV sidekick. Others in the cast were Pert Kelton, Mary Schipp, Jack Albertson, Arthur Q. Bryan, Ed Begley and announcer Frank Gallop. Sponsored by Philip Morris, it aired on NBC from March 11, 1947, until April 13, 1948.
His last radio series was The Texaco Star Theater, which began September 22, 1948 on ABC and continued until June 15, 1949, with Berle heading the cast of Stang, Kelton and Gallop, along with Charles Irving, Kay Armen, and double-talk specialist Al Kelly. It employed top comedy writers (Nat Hiken, brothers Danny and Neil Simon, Leo Fuld, Aaron Ruben), and Berle later recalled this series as "the best radio show I ever did... a hell of a funny variety show." It served as a springboard for Berle's rise as television's first major star.
In 1948, NBC decided to bring Texaco Star Theater from radio to television, with Berle as one of the show's four rotating hosts. For the fall season, NBC named Berle the permanent host. His highly visual, sometimes outrageous vaudeville style proved ideal for the burgeoning new medium. Berle and Texaco owned Tuesday nights for the next several years, reaching the number one slot in the Nielsen ratings and keeping it, with as much as an 80% share of the recorded viewing audience. Berle and the show each won Emmy Awards after the first season. Fewer movie tickets were sold on Tuesdays. Some theaters, restaurants and other businesses shut down for the hour or closed for the evening so their customers wouldn't miss Berle's antics
Berle's autobiography notes that in Detroit, "an investigation took place when the water levels took a drastic drop in the reservoirs on Tuesday nights between 9 and 9:05. It turned out that everyone waited until the end of the Texaco Star Theater before going to the bathroom."
Berle is credited for the huge spike in the sale of TV sets. (Other comedians turned this into a punchline: "I sold mine, my uncle sold his...") After Berle's show began, set sales more than doubled, reaching two million in 1949. His stature as the medium's first superstar earned Berle the sobriquet "Mr. Television."
He also earned a slightly more familiar nickname after ending a 1949 broadcast with a brief ad-libbed remark to children watching the show: "Listen to your Uncle Miltie and go to bed." 
Berle asked NBC to switch from live broadcasts to filmed shows, to make possible future reruns and residuals, and he was not happy when NBC showed little interest. NBC did consent to make a kinescope of each show — a reference copy filmed directly off a TV screen.
He also risked his newfound TV stardom at its zenith to challenge Texaco when the sponsor tried to prevent black performers from appearing. In his autobiography, Berle recalled the incident:
Another thing that was a constant anger to me was that I didn't have approval on the acts and performers I wanted on the show. I remember clashing with the sponsor and the advertising agency and the sponsor over my signing the Four Step Brothers for an appearance on the show. The only thing I could figure out was that there was an objection to black performers on the show, but I couldn't even find out who was objecting. "We just don't like them," I was told, but who the hell was "we"? Because I was riding high in 1950, I sent out the word: "If they don't go on, I don't go on." At ten minutes of eight — ten minutes before show time — I got permission for the Step Brothers to appear. If I broke the color-line policy or not, I don't know, but later on I had no trouble booking Bill Robinson or Lena Horne."
Texaco pulled out of sponsorship of the show in 1953. Buick picked it up, prompting a renaming to The Buick-Berle Show, the program's format retooled to show the backstage preparations to put on a variety show. Critics generally approved the changes, but Berle's ratings continued to fall and Buick pulled out after two seasons. By the time the again-renamed Milton Berle Show finished its only full season, Berle was already becoming history — though his final season was host to two of Elvis Presley's earliest television appearances, April 3, 1956, & June 5, 1956.
NBC finally cancelled the Berle show in June 1956, after the controversy caused by Elvis Presley's uninhibited performance of "Hound Dog." Berle later appeared in the Kraft Music Hall series, but NBC was finding increasingly fewer showcases for its one-time superstar. By 1960, he was reduced to hosting a game show, Jackpot Bowling, delivering his quips between the efforts of bowling contestants.
He appeared in numerous films, including Always Leave Them Laughing (1949) with Virginia Mayo and Bert Lahr; Let's Make Love, with Marilyn Monroe and Yves Montand (1960); It's a Mad, Mad, Mad, Mad World (1963); The Loved One (1965); The Oscar (1966); Lepke (1975); Woody Allen's Broadway Danny Rose (1984) and Driving Me Crazy (1991).
Freed in part from the obligations of his NBC contract, Berle was signed in 1966 to a new, weekly variety series on ABC. The show failed to capture a large audience and was cancelled after one season. He later appeared as guest villain Louie the Lilac on ABC's Batman series. Other memorable guest appearances included stints on The Lucy Show, The Jackie Gleason Show, Laugh-In, The Sonny & Cher Comedy Hour, The Hollywood Palace, F Troop, Fantasy Island, and The Jack Benny Show.
Like his contemporary Jackie Gleason, Berle proved a solid dramatic actor and was acclaimed for several such performances, most notably his lead role in "Doyle Against The House" on The Dick Powell Show in 1961, a role for which he later received an Emmy nomination. He also played the part of a blind survivor of an airplane crash in Seven in Darkness, the first in ABC's popular Movie of the Week series.
During this period, Berle was named to the Guinness Book of World Records for the greatest number of charity performances made by a show-business performer. Unlike the high-profile shows done by Bob Hope to entertain the troops, Berle did more shows, over a period of 50 years, on a lower-profile basis. Berle received an award for entertaining at stateside military bases in World War I as a child performer, in addition to traveling to foreign bases in World War II and Vietnam. The first charity telethon (for the Damon Runyon Cancer Research Foundation
) was hosted by Berle in 1949
A permanent fixture at charity benefits in the Hollywood area, he was instrumental in raising millions for charitable causes.
Milton Berle was a guest star on The Muppet Show, where he was memorably upstaged by the heckling theatre box critics Statler and Waldorf.
Another well-known incident of upstaging occurred during the 1982 Emmy Awards, when Berle and Martha Raye were the presenters of the Emmy for Outstanding Writing. Berle was reluctant to give up the microphone to the award's recipients, from Second City Television, and interrupted actor Joe Flaherty's acceptance speech several times. After Flaherty would make a joke, Berle would reply sarcastically "Oh, that's funny." However the kindly, smiling Flaherty's response "Go to sleep, Uncle Miltie" flustered Berle who could only reply with a stunned "What...?" SCTV later created a parody sketch of the incident, in which Flaherty beats up a Berle look-alike, shouting, "You'll never ruin another acceptance speech, Uncle Miltie!"
One of his most popular performances in his later years was guest starring in 1993 in The Fresh Prince of Bel-Air as womanizing, wise-cracking patient Max Jakey. Most of his dialogue was improvised and he shocked the studio audience by mistakenly blurting out a curse word.
Berle appeared in drag in the video for "Round and Round" by the 1980s metal band Ratt (his nephew Marshall Berle was then their manager).
Berle was again on the receiving end of an onstage jibe at the 1993 MTV Video Music Awards where RuPaul notoriously responded to Berle's reference of having once worn dresses himself (during his old television days) with the quip that Berle now wore diapers. A surprised Berle replied, "Oh, we're going to ad lib? I'll check my brain and we'll start even."
Unlike many of his peers, Berle's off-stage lifestyle did not include drugs or drinking, but did include cigars, a "who's who" list of beautiful women, and a lifelong addiction to gambling, primarily horse racing. Some felt his obsession with "the ponies" was responsible for Berle never amassing the wealth or business success of others in his position.
Berle was also famous within show business for the rumored size of his penis. Phil Silvers once told a story about standing next to Berle at a urinal, glancing down, and quipping, "You'd better feed that thing, or it's liable to turn on you!" Saturday Night Live writer Alan Zweibel, who had written many Friars Club jokes about Berle's penis for other comedians, described being treated to a private showing: "He just takes out this— this anaconda. He lays it on the table and I'm looking into this thing, right? I'm looking into the head of Milton Berle's dick. It was enormous. It was like a pepperoni. And he goes, 'What do you think of the boy?' And I'm looking right at it and I go, 'Oh, it's really, really nice.'" At a memorial service for Berle at the New York Friars' Club, Freddie Roman solemnly announced, "On May 1st and May 2nd, his penis will be buried.
Berle was known to have a colorful vocabulary and few limits on when it was used. Surprisingly, however, he "worked clean" for his entire onstage career, except for the infamous Friars Club all-male, private celebrity roasts. Berle often criticized younger comedians like Lenny Bruce and George Carlin about their X-rated humor, and challenged them to be just as funny without the four-letter words.
Hundreds of younger comics, including several comedy superstars, were encouraged and guided by Berle. Despite some less than flattering (and true) stories told about Berle being difficult to work with; his son, Bill, maintains that Berle was a source of encouragement and technical assistance for many new comics. Uncle Milty's son Bob backs up his brother's statement. He was present many times during Berle's Las Vegas shows and television guest appearances. Milton aided Fred Travelena, Ruth Buzzi, John Ritter, Marla Gibbs, Lilly Tomlin, Dick Shawn and Will Smith. At a taping of a Donny and Marie hour, for example, Donny and Marie Osmond recited a scripted joke routine to a studio audience, to little response. The director asked for a retake, and the Osmonds repeated the act, word for word, to even less response. A third attempt, with no variation, proved dismal — until Milton Berle, off-camera, went into the audience, pantomiming funny faces and gestures. Ever the professional, Berle timed each gesture to coincide with an Osmond punchline, so the dialogue seemed to be getting the maximum laughs.
Berle once made fun of Charlie Parker and Miles Davis while they were on stage, calling them "headhunters". Davis said that he confronted Berle later on in life and that Berle apologized.
Berle was well known among his peers to have one of the largest joke collections in the world, which Berle estimated to be between five and six million jokes. Berle had a reputation for stealing material from other comedians, which eventually became known to the public. Bob Hope quipped onstage with Berle, that he "never heard a joke he didn't steal." "Uncle Miltie" would then mug for the cameras with an exaggerated innocent face. On more than one occasion, Berle would commend a co-star for a punchline, saying, "I wish I'd said that," to which the co-star would invariably reply, "Oh, you will." Columnist Walter Winchell famously labelled Berle with the unflattering nickname "The Thief of Bad Gags." Upon being accused of stealing jokes from Berle, Jack Benny once quipped, "When you take a joke away from Milton Berle, it's not stealing, it's repossessing."
Occasional claims by Berle and others that these jokes were transferred to computer media are suspect, as a member of Berle's family verified that the majority of them were on sheets and scraps of paper and index cards in a vast, disorganized collection amassed over decades, well before personal computers. The books Milton Berle's Private Joke File and The Rest of the Best of Milton Berle's Private Joke File each contained 10,000 of these jokes.
After twice marrying and divorcing Joyce Mathews, a showgirl, Berle married, in 1953, Ruth Cosgrove, a onetime publicist; she died in 1989. He married his fourth wife, Lorna Adams, a fashion designer, in 1991. He had two children, Victoria (adopted by Berle and Mathews) and William (adopted by Berle and Cosgrove). Berle also had two stepdaughters from his marriage to Lorna Adams—Leslie and Susan Brown, who is married to actor Richard Moll.
In later life, Berle found solace in Christian Science and called himself a Jew and a Christian Scientist.
Berle retained co-ownership of his NBC programs and specials, but the other owner, NBC, had forgotten them. In 2000, Berle approached NBC about making the episodes available on home video, through infomercials. He discovered that NBC no longer had the programs on file.
The 91-year-old Berle made national headlines when he sued NBC for $30,000,000, claiming the network's negligence in deliberately or accidentally losing or destroying the Berle shows. Berle itemized the loss of 84 Texaco hours, 32 Buick shows, and 12 prime-time specials. NBC scoured the shelves for the missing films, which turned up two months later in the network's Burbank, California facility. All but four of the films were recovered.
At the time of the announcement, Berle's wife said the tumor was growing so slowly that it would take ten to twelve years to affect him in any significant or life-threatening way. Unfortunately, less than one year after the announcement, Berle died on March 27, 2002, at the age of 93 in Los Angeles, California. Director Billy Wilder and comedian Dudley Moore also died that day, and comedian Tony Randall called it "the day comedy died" (a play on the expression The Day the Music Died).Berle left detailed arrangements to be buried with his third wife, Ruth, at Mount Sinai Memorial Park Cemetery in Burbank. His fourth and last wife, Lorna Adams, altered the plan so that he was cremated and interred at Hillside Memorial Park Cemetery in Culver City, California. In addition to his wife, Berle was survived by an adopted daughter, Victoria, born in 1945; adopted son, William, born in 1961; and Bob Williams, a biological son, born in 1951. William Berle and Brad Lewis collaborated on the biography, My Father, Uncle Miltie (Barricade Books, 1999).