After years in radio, Allen conceived a local New York talk-variety TV program in 1953 for what is now WNBC-TV. The following year, on September 27, 1954, the show went on the full NBC network as The Tonight Show, with fellow radio personality Gene Rayburn as the original announcer/sidekick. The show ran from 11:15 pm to 1:00 am on the East Coast.

While Pat Weaver, the developer of The Today Show, is often credited as Tonight's creator as well, Allen often pointed out that the show had already been "created"—by himself—as a local show. "This is Tonight, and I can't think of too much to tell you about it except I want to give you the bad news first: this program is going to go on forever," Allen told his nationwide audience that first evening. "Boy, you think you're tired now. Wait until you see one o'clock roll around."
Allen also joked that they selected the Hudson Theatre on 44th Street in Manhattan for the program because "I think it sleeps around 800 people."

It was as host of The Tonight Show that Allen pioneered the "man on the street" and audience-participation comedy bits that have become commonplace in late-night TV. In 1956, while still hosting Tonight, Allen added a Sunday-evening variety show. The Allen programs helped nurture the careers of singers Steve Lawrence and Eydie Gorme and Sammy Davis, Jr. Allen also provided a nationwide audience for his famous "man on the street"— comics such as Ernie Kovacs, Pat Harrington, Jr., Don Knotts, Louis Nye, Bill Dana, Dayton Allen, and Tom Poston.

Allen remained host of Tonight until 1957, when he left. (After an ill-fated nightlife-oriented replacement Tonight! America After Dark, the old Tonight format returned later in the year with Jack Paar at the helm.) Allen amassed a huge windfall for his work because he had opted to be paid in Polaroid stock.

Allen went on to host a slew of television programs up until the 1980s, including the game show I've Got a Secret and The New Steve Allen Show in 1961. He was a regular on the extremely popular panel game show What's My Line? from 1953 to 1954 and returned as a guest panelist until the series' end in 1967.

Allen was also a composer who supposedly wrote over 7,000 songs. In one famous stunt, he made a bet with singer-songwriter Frankie Laine that he could write fifty songs a day for a week. Composing on public display in the window of a Hollywood music store, Allen met the quota, winning $1,000 from Mr. Laine. One of the songs "Let's Go to Church Next Sunday" was recorded by both Perry Como and Margaret Whiting. Allen's best known songs are "This Could Be the Start of Something Big" and "The Gravy Waltz," which won a Grammy Award in 1963 for best jazz composition. Allen was also an actor, appearing in such films as The Benny Goodman Story (1955).

Allen was also the producer of the award-winning PBS series Meeting of Minds, a "talk show" with notable historical figures, with Steve Allen serving as host. This series pitted Socrates, Marie Antoinette, Thomas Paine, Sir Thomas More, Attila the Hun, Karl Marx, Emily Dickinson, Charles Darwin, Galileo Galilei, and other historical figures in dialogue and argument. A proposed revival of this show was rejected as "too cerebral."

He was also an accomplished comedy writer and author of over fifty books, including Dumbth, a commentary on the American educational system and Steve Allen on the Bible, Religion, and Morality.

Allen was a secular humanist and Humanist Laureate for the Academy of Humanism, a member of CSICOP and the Council for Secular Humanism. He was a student and supporter of general semantics, recommending it in Dumbth and giving the Alfred Korzybski Memorial Lecture in 1992. Allen was a supporter of world government and served on the World Federalist Association Board of Advisers. [1]

In spite of his liberal position on free speech, his later concerns about the smuttiness he observed on television caused him to make proposals restricting the content of programs, allying himself with the Parents Television Council. He was also notoriously contemptuous of rock 'n' roll music. On one occasion, in a spirit of not-so-subtle mockery, he had Elvis Presley wear a top hat and tails while singing "Hound Dog" to an actual hound, who was similarly attired. Allen also was known to "interpret" the lyrics of actual rock songs to his audience as little more than a series of grunts.

Allen's second wife was actress Jayne Meadows, by whom he had one son. They were married from 1954 until his death in 2000. He died of a cardiac disease triggered by a previous minor traffic accident the same day (October 30, 2000) at the age of 78 and is interred in the Forest Lawn Memorial Park at Hollywood Hills in Los Angeles, California.

Steve Allen has two stars on the Hollywood Walk of Fame: a TV star at 1720 Vine St. and a radio star at 1537 Vine St.