Leguizamo was born in Bogotá, the son of Alberto and Luz Leguizamo. His father was once an aspiring film director and studied at Cinecittà, but eventually dropped out due to lack of finances. According to Leguizamo, his paternal grandfather was of Italian and Puerto Rican descent, and his maternal grandmother was Lebanese. He has also described himself as being of Amerindian and Mestizo heritage. On June 10, 2011, Leguizamo's father declared in an interview with New York Hispanic newspaper El Diario that he is Colombian and not Puerto Rican, and that Leguizamo is therefore not half Puerto Rican as he has always stated. Leguizamo had always declared that he was Puerto Rican on his father's side, which was one of the reasons he was selected as the Puerto Rican Day Parade Global Ambassador of the Arts. In response to his father's allegations, Leguizamo reiterated that his grandfather was of Puerto Rican descent. A National Puerto Rican Day Parade spokesman stated that Leguizamo would keep his ambassadorship. He marched in the parade on June 12, 2011.
When Leguizamo was four years old, his family immigrated to the United States, and lived in various neighborhoods in Queens, New York, including Jackson Heights. He later credited growing up as one of the first Latino children in the neighborhood as formative in his acting ability: "It was tough. There were lots of fights. I would walk through a park and be attacked, and I had to defend myself all the time. But this helped me to become funny so that I wouldn’t get hit." Leguizamo attended the Joseph Pulitzer Middle School (I.S.145) and later the Murry Bergtraum High School. As a student at Murry Bergtraum, he wrote comedy material and tested it on his classmates. He was voted "Most Talkative" by his classmates. After graduating from high school, he began his theater career as an undergraduate at NYU's Tisch School of the Arts, from which he eventually dropped out in favor of a career in stand-up comedy. Post-NYU, Leguizamo enrolled at LIU Post, where he took theater classes.
Leguizamo started out as a stand-up comic doing the New York nightclub circuit in 1984. He made his television debut in 1986 with a small part in Miami Vice. His other early roles include: a friend of Madonna's boyfriend in her "Borderline" video (1984); Mixed Blood (1985), Casualties of War (1989), a terrorist in Die Hard 2 (1990), Hangin' with the Homeboys (1991), the robber in Regarding Henry (1991), Super Mario Bros (1993) and Night Owl (1993).
In 1992, he starred in Whispers in the Dark as John Castillo. In 1993 Leguizamo was offered the lead part as Luigi in the film Super Mario Bros., based on the Mario video game franchise. Despite being considered a critical and financial failure universally, the film started his acting career in Hollywood and became one of his memorable roles. It also provided a boost to his career, allowing him to appear in better comedic roles in the following years. That same year, he had a prominent role in Brian De Palma's Carlito's Way as Carlito Brigante's nemesis, "Benny Blanco from the Bronx," which also boosted his career in serious roles.
Leguizamo also starred in Romeo + Juliet as Tybalt Capulet, as Violator in Spawn, Cholo in Land of the Dead, and Pestario 'Pest' Vargas in The Pest, the latter being one of his few roles as a lead actor in a studio film. In 1995, he starred as drag queen Chi-Chi Rodriguez in To Wong Foo, Thanks for Everything! Julie Newmar for which he received a Golden Globe Nomination for Best Supporting Actor, and starred in the 1996 action film Executive Decision as Captain Rat. In 2002, he starred in the movie Empire. To promote the 2001 movie Moulin Rouge!, he appeared on a celebrity edition of the US version of Who Wants to Be a Millionaire? with Kelly Ripa, Kevin Sorbo, Alfre Woodard, Martin Short and Chevy Chase. Appearing as the first celebrity to sit in the hot seat, he eventually tried for $125,000, but got the answer wrong. Later in 2002, on the syndicated version, a question about the movie featured his character and Meredith Vieira mentioned that Leguizamo had played Lautrec and had been on the show.
In 2002, he voiced Sid the Sloth for the film Ice Age, reprising the role for the sequels Ice Age: The Meltdown, Ice Age: Dawn of the Dinosaurs, Ice Age: Continental Drift and Ice Age: Collision Course. The game versions of the films also used his voice. In 2003, he voice-acted Globox from Rayman 3: Hoodlum Havoc. Leguizamo portrayed Paul in the Brad Anderson thriller film Vanishing on 7th Street. In 2007, he played Michael Beltran in the movie The Babysitters. In 2008, he co-starred in the movie The Happening, written and directed by M. Night Shyamalan. In 2014 Leguizamo starred alongside Jon Favreau in Chef. Also in 2014, he played a drug dealer in the Jesse Eisenberg and Kristen Stewart movie American Ultra.
In October 2013, Leguizamo started filming for The Crash, starring alongside Frank Grillo, AnnaSophia Robb, Dianna Agron, Ed Westwick, Minnie Driver, Mary McCormack, Christopher McDonald and Maggie Q. The film is directed by Aram Rappaport and produced by Hilary Shor, Atit Shah and Aaron Becker. The Crash is set to release January 13, 2017.
In 1995 Leguizamo created, produced, wrote, and starred in the 1995 Latino-oriented variety show called House of Buggin' on Fox Television. Some audiences saw this as the Latino version of In Living Color. The show showcased Leguizamo's well-known ability to assume a wide variety of colorful, energetic characters, but due to poor ratings the show ran less than one season.
In 2000, Leguizamo portrayed both Genies in Arabian Nights, a TV mini-series adaptation of the epic One Thousand and One Nights.
During the 2005–06 television season, Leguizamo joined the cast of the show ER, playing the emotionally disturbed Dr. Victor Clemente, a new attending who is keen on introducing the staff of County General to better ways of treating patients and cutting-edge technology. Clemente, however, was plagued with personal problems and was fired from the hospital near the end of the season. Dr. Clemente's departure from the show was a blessing for Leguizamo. He revealed to CraveOnline that he was not happy working on the television program. "I was depressed doing ER," he admitted, "I started gaining weight, I was eating doughnuts, I started smoking again. I’m eating McDonald's, things that I know when I’m depressed I do. I tried to kill myself internally."
In 2005, he guest starred on Dora the Explorer as Captain Pirate Piggy. In 2006, Leguizamo starred in the television pilot for Edison, a 2006 CBS drama about an Los Angeles detective (played by Leguizamo) who relied on impersonations and disguises to solve crimes. Other cast members included Currie Graham and Deidrie Henry. Kevin Rodney Sullivan directed from a script by Ron Milbauer and Terri Hughes. Leguizamo and David Hoberman also served as executive producers.
In July 2007, Spike TV aired its drama series The Kill Point, which starred Leguizamo, Donnie Wahlberg, and Michael Hyatt. The show was an eight-part series revolving around ex-war veterans whose bank robbery went wrong, thus ending in a hostage situation. Despite high ratings, The Kill Point was not renewed for a second season.
In 2010, Leguizamo also guest starred on The Electric Company as himself, rhyming about commas and quotation marks.
In 2012, Leguizamo was cast as Derek Trotter in the American remake of the British BBC sitcom Only Fools and Horses.
In 2016, he played the role Ozzy Delvecchio in the second season of the Netflix original series Bloodline.
In 1991, Leguizamo also wrote and took part in the Off-Broadway production Mambo Mouth, where he played seven different characters. Mambo Mouth won an Obie Award and an Outer Critics Award. He was listed as one of 12 "Promising New Actors of 1991" in "John Willis' Screen Worlds Vol. 43".
In 1993, Leguizamo wrote and participated in Spic-O-Rama, where he made fun of the stereotyping of Latinos in the United States. The production won a Drama Desk Award and four Cable ACE Awards. Both Mambo Mouth and Spic-O-Rama were later filmed for presentation on HBO.
In 1998, he debuted on Broadway in the production of Freak, a semi-autobiographical one-person play that was recorded for HBO and released on October 10, 1998, with Spike Lee sitting in as director. The show won him the Drama Desk Award for Outstanding One-Person Show.
In 2002, he wrote and performed in Sexaholix... A Love Story, which explained his love life and how he started his own family.
In June 2010, Leguizamo opened his semi-autobiographical one-man theater show, Klass Klown (later renamed Ghetto Klown), based on his memoir Pimps, Hos, Playa Hatas, and All the Rest of My Hollywood Friends: My Life. After the show ran at various theaters in the United States and Leguizamo performed an "unplugged" version of it under the title John Leguizamo Warms Up at a Chicago theater, it opened on Broadway in March 2011 at the Lyceum Theatre. The show, about Leguizamo's path from obscurity to stardrom, opened to many positive reviews and was extended through July 10, 2011. A CD of the show was released. In 2011, Leguizamo received the Outer Critics Circle Award for Outstanding Solo Performance and the Drama Desk Award for Outstanding Solo Performance for his performance in the show. In September 2011, Leguizamo began an international tour of Ghetto Klown in Los Angeles. On July 13, 2012, PBS debuted Tales From a Ghetto Klown, a documentary about Leguizamo's life and the show's development. On November 16, 2013 John taped Ghetto Klown at The New Jersey Performing Arts Center in Newark, NJ for HBO.
In 2001, RCA/BMG Records released John Leguizamo LIVE, a CD compilation of Leguizamo's stage routines. Among the bits are a primer Leguizamo gives on the history and culture of Latinos in America, which with the dubious tale of the mating of an Inca princess with a Spanish conquistador, thus creating the original dysfunctional Latin family, each member of which is voiced by Leguizamo. The CD also includes a musical intermission, with two salsa/hip-hop tunes, "The Night Before Christmas" and "Gotta Get Some", and footage from Leguizamo's tours and two interactive games, "Spanish Fly Pick-Up Line".
In October 2006, Leguizamo's memoir, Pimps, Hos, Playa Hatas and All the Rest of My Hollywood Friends: My Life, was released. During an interview on Late Night with Conan O'Brien, he stated that his memoir was very candid about experiences involving other celebrities he had worked with. He stated that working with Arnold Schwarzenegger on Collateral Damage (2002) was one of the most enjoyable experiences he'd had as an actor, that Schwarzenegger's accent let him say things that others would think were sexist or homophobic if said by someone else, that Steven Seagal was an egotist with diva tendencies, that Kurt Russell continuously called him a "faggot", and that Leonardo DiCaprio was a "patron of prostitutes".
In October 2015, Abrams ComicArts published the graphic novel adaptation of Leguizamo's one-man Broadway show, Ghetto Klown. As with the live show, the graphic novel explores the actor/comedian's life and career, beginning with his adolescence in Queens, New York, his involvement in '80s avant-garde theater, his feature film career, and some of the colorful characters he encountered throughout his life. Leguizamo describes the work thusly: "Ghetto Klown is the history that I probably never should have told anyone but my therapist, but it's a real lesson that even if you suffer a certain amount (a lot) of self-doubt and anxiety, you can still accomplish great things. It’s a lesson I'm really excited to impart to a whole new audience." The comic is illustrated by Christo Cassano.
Leguizamo married actress Yelba Osorio in 1994. They divorced in 1996.
He married Justine Maurer, a costumer on Carlito's Way, in a Catholic-Jewish ceremony on June 28, 2003; he is Catholic and Maurer is Jewish. They have two children, daughter Allegra Sky Leguizamo (born 1999) and son Ryder Lee "Lucas" Leguizamo (born 2000). They live in Manhattan, New York.
In 2008, Leguizamo received the Rita Moreno HOLA Award for Excellence from the Hispanic Organization of Latin Actors (HOLA). In 2011, he received the Made in NY Award from New York City.