In the mid-1970s, Martin made frequent appearances as a stand-up comedian on The Tonight Show Starring Johnny Carson.[13] That exposure, together with appearances on The Gong Show, HBO's On Location and NBC's Saturday Night Live (SNL) (on which, despite a common misconception, he was never a cast member) led to his first of four comedy albums, Let's Get Small. The album was a huge success; one of its tracks, "Excuse Me", helped establish a national catch phrase. His next album, A Wild and Crazy Guy, was an even bigger success, reaching the #2 spot on the sales chart in the U.S. and featured another catch phrase (the album's title), also featured in a Saturday Night Live sketch in which Martin and Dan Aykroyd played a couple of bumbling Czechoslovak would-be playboys, the Festrunk Brothers. The album ended with a song "King Tut", sung and written by Martin and released as a 45 RPM single during the King Tut craze that accompanied the extremely popular traveling exhibit of the Egyptian king's tomb artifacts; the single reached #17 in 1978. The song was backed by the "Toot Uncommons" (they were actually members of the Nitty Gritty Dirt Band). The album was a million seller. Both albums won Grammys for Best Comedy Recording in 1977 and 1978, respectively. Steve performed "King Tut" on the April 22, 1978 edition of SNL. In his comedy albums, Martin's stand-up comedy was clearly self-referential and sometimes self-mocking. It mixes philosophical riffs with sudden spurts of "happy feet", banjo playing with balloon depictions of concepts like venereal disease. His style is off-kilter and ironic, and sometimes pokes fun at stand-up comedy traditions, such as Martin opening his act by saying, "I think there's nothing better for a person to come up and do the same thing over and over for two weeks. This is what I enjoy, so I'm going to do the same thing over and over and over....I'm going to do the same joke over and over in the same show, it'll be like a new thing." Or: "Hello, I'm Steve Martin, and I'll be out here in a minute . . . "

During his frequent SNL guest appearances, Martin popularized the "quote" gesture, which uses four fingers to make double quote marks in the air.

Martin related that in one comedy routine (used on the Comedy Is Not Pretty! LP) he denies that he is named "Steve Martin"; his real name is "Gern Blanston". He said that the riff took on a life of its own, and there is even a Gern Blanston website, and for a time a rock band used the words as its name.

While on Saturday Night Live, Martin became very close with several of the cast members. One was Gilda Radner. On the day Radner died from ovarian cancer in 1989, Martin was to host SNL. Instead of delivering the intended monologue, Martin showed a video clip of him and Radner appearing in a 1978 sketch. He introduced the clip to the audience and became overcome with grief and started to cry.

By the end of the 1970s, Martin had acquired the kind of following normally reserved for rock stars, with his tour appearances typically occurring at sold-out arenas filled with tens of thousands of screaming fans. But unknown to his audience, stand-up comedy was "just an accident" for him. His real goal was to get into film.[9] Martin's first film was a short, The Absent-Minded Waiter (1977). The seven-minute long film, also featuring Buck Henry and Teri Garr, was written by and starred Martin. The film was nominated for an Academy Award as Best Short Film, Live Action. His first feature film appearance was in the musical Sgt. Pepper's Lonely Hearts Club Band, where he sang The Beatles' "Maxwell's Silver Hammer". In 1979, Martin co-wrote and starred in his first full-length movie, The Jerk, directed by Carl Reiner. The movie was a huge success, grossing over $73 million on a budget of far less than that amount.

The success of The Jerk opened more doors for Martin. Stanley Kubrick met with him to discuss the possibility of Martin starring in a screwball comedy version of Traumnovelle (Kubrick later changed his approach to the material, the result of which was 1999's Eyes Wide Shut). Martin was executive producer for Domestic Life, a prime-time television series starring friend Martin Mull, and a late-night series called Twilight Theater. It emboldened Martin to try his hand at his first serious film, Pennies From Heaven, a movie he was anxious to do because of the desire to avoid being typecast. To prepare for that film, Martin took acting lessons from director Herbert Ross, and spent months learning how to tap dance. The film was a financial failure; Martin's comment at the time was "I don't know what to blame, other than it's me and not a comedy."

Martin was in three more Reiner-directed comedies after The Jerk: Dead Men Don't Wear Plaid in 1982, The Man with Two Brains in 1983 and All of Me in 1984, possibly his most critically acclaimed comic performance to date. In 1986, Martin joined fellow Saturday Night Live veterans Martin Short and Chevy Chase in ¡Three Amigos!, directed by John Landis, and written by Martin, Lorne Michaels, and singer-songwriter Randy Newman. It was originally entitled The Three Caballeros and Martin was to be teamed with Dan Aykroyd and John Belushi. In 1986, Martin was in the movie musical film version of the hit off-Broadway play Little Shop of Horrors (based on a famous B-movie), as a sadistic dentist, Orin Scrivello. The film also marked the first of three films teaming Martin with actor Rick Moranis. In 1987, Martin joined comedian John Candy in the John Hughes movie Planes, Trains & Automobiles. That same year, the Cyrano de Bergerac adaptation Roxanne, a film Martin co-wrote, won him a Writers Guild of America, East award and more importantly, the recognition from Hollywood and the public that he was more than a comedian. In 1988, he performed in the Frank Oz comedy Dirty Rotten Scoundrels alongside Michael Caine.

Martin starred in the Ron Howard film Parenthood, with Moranis in 1989. He later met with Moranis to make the Mafia comedy My Blue Heaven in 1990. In 1991, Martin starred in and wrote L.A. Story (a romantic comedy, in which the female lead was played by his then-wife Victoria Tennant) and was a member of the ensemble existentialist tragedy Grand Canyon that were both about life in Los Angeles. In a serious role, Martin played a tightly wound Hollywood film producer trying to recover from a traumatic robbery that left him injured. In contrast to the serious tone of Grand Canyon, Martin also appeared in a remake of the comedy Father of the Bride in 1991 (followed by a sequel in 1995). He also starred in the 1992 comedy film HouseSitter, with Goldie Hawn and Dana Delany. Martin also starred with Eddie Murphy in the 1999 comedy Bowfinger.

In David Mamet's 1997 thriller, The Spanish Prisoner, Martin played a darker role as a wealthy stranger who takes a suspicious interest in the work of a young businessman (Campbell Scott). In 1999, Martin and Hawn starred in a remake of the 1970 Neil Simon comedy, The Out-of-Towners. By 2003, Martin ranked 4th on the box office stars list, after co-starring in Bringing Down The House and starring in Cheaper By The Dozen, each of which earned over $130 million at U.S. theaters. Both were family comedies.

In 2005, Martin wrote and starred in Shopgirl, based on his own novella. Martin played a wealthy businessman who strikes up a romance with a Saks Fifth Avenue counter girl (Claire Danes). He also starred in Cheaper by the Dozen 2 that year. Martin also starred in the 2006 installment of The Pink Panther, attempting to stand in Peter Sellers' shoes as the bumbling Inspector Clouseau. The sequel is scheduled to be released in early 2009. His most recent work to date is the 2008 comedy Baby Mama, where he plays a holistic and self-absorbed founder of a health foods company.

In 2008, he produced the dramatic thriller Traitor, starring Don Cheadle. Martin is credited as an executive producer and writing the story.