In 1988, Seagal began work on his first film, Above the Law (titled Nico in Europe), with director Andrew Davis and reportedly as a favor to a former aikido student, the agent Michael Ovitz, who believed he could make anyone a star.Following its success, Seagal made three more movies – Hard to Kill, Marked for Death, and Out for Justice – that were box office hits, making him an action hero. Later, he achieved wider, mainstream success in 1992 with the release of Under Siege (1992). That film reunited Seagal with director Andrew Davis, and was a blockbuster in the U.S. and abroad, grossing $156.4 million worldwide.

After the success of Under Siege, Seagal made his directorial debut with On Deadly Ground (1994) in which he starred with Michael Caine. The movie did badly with audiences and critics, and was an estimated financial loss of $50 million to make, while grossing less than $39 million in the U.S.

To regain popularity, he filmed a sequel to his most successful film Under Siege titled Under Siege 2: Dark Territory (1995) and the cop drama The Glimmer Man (1996). In 1996, he had his first supporting role, in the Kurt Russell film Executive Decision (1996), which featured him as in a starring role, but kept secret his character's fate. Then, he again made an environmentally-conscious film, Fire Down Below (1997), wherein he was an EPA agent fighting industrialists dumping toxic waste in the Kentucky hills, but the movie was commercially unsuccessful. This film ended his original multi-picture contract with Warner Bros., and because of its disaster, his contract was not renewed.

The next year, Seagal made The Patriot, another environmental thriller which was his first direct-to-video release in the United States (though it was released theatrically in most of the world). Seagal produced this film with his own money, and the film was shot on-location on and near his farm in Montana.

After taking a couple years to produce Prince of Central Park, Seagal returned to cinema screens with the release of Exit Wounds in March 2001. The film had fewer martial arts scenes than Seagal's previous films, but it was a commercial success, taking almost $80 million worldwide. However, he was unable to capitalize on this success and his next two projects were both critical and commercial failures. Ticker co-starring Tom Sizemore and Dennis Hopper, and filmed in San Francisco before Exit Wounds, went straight to DVD while Half Past Dead, starring rap star Ja Rule, made less than $20 million worldwide.

As of May 2008[update], all of the films Seagal has made since 2003 have been released direct-to-video (DTV) in North America, with only limited theatrical releases in the rest of the world. Though Seagal is credited as a producer (and sometimes a writer) on many of these DTV movies, it is unclear how deeply involved he was in their production - his voice is often dubbed in by another actor as seen in the film Attack Force and a double is used in almost any scene where his face is not shown clearly. The most notable stunt doubles are in his films Black Dawn, Belly of the Beast, Out of Reach and Submerged.

His latest direct-to-video films include Urban Justice (2007) Pistol Whipped (2008) Against The Dark (2008) Kill Switch (2008) and Ruslan (2008). He has just finished filming The Keeper (2008) for a projected 2009 release. His latest film is called Dangerous Man (2009) and is currently in pre-production. This will be the third time that Seagal has worked with Voltage Pictures. Filming is expected to begin around Feb/March 2009. Seagal will then work for director Albert Pyun in the sword and sorcerer film The Destroyer of Souls, also starring Charles Durning, Tom Selleck and Ralph Macchio. Filming will take place in Argentina and in Brazil (locations will include Paraiba and Ceara).