After his parents' divorce, Muniz moved to California with his mother. He appeared in commercials and made his film debut in the made-for-television movie, To Dance With Olivia (1997), starring Lou Gossett Jr. The same year, he appeared in the CBS Hallmark Hall of Fame presentation of What the Deaf Man Heard. A small role in the film Lost & Found (1999) led up to the breakthrough role, which would make him a familiar face in millions of households.

Film & TV career FOX premiered Malcolm in the Middle on January 9, 2000, as a mid-season replacement, and the show was quickly swamped with accolades. The premiere episode was watched by 23 million people; and the 2nd episode by 26 million people. Muniz anchored the show with his narration and his central role in many of the series' plots, although he has said that he does not consider himself a comic actor and does not find himself funny. He was nominated for Golden Globes in 2000 and 2001, the Emmy Awards in 2001, and was honored with the Hollywood Reporter "Young Star Award" for his work in the series.

Throughout his television career, Muniz made guest appearances on the shows Lizzie McGuire, Sabrina, the Teenage Witch, and MADtv. His first starring role in a feature film was as "Willie Morris" in the family period piece My Dog Skip (2000), released around the time of the Malcolm pilot. Muniz then contributed a voice to the animal cast of Dr. Dolittle 2 (2001). He had a moderate-sized hit with the 2002 release Big Fat Liar, which teamed him with teen actress Amanda Bynes, as a pair of students seeking revenge on a sleazy movie producer (Paul Giamatti). He was also part of the ensemble for the gang film, Deuces Wild, released the same year.

Muniz subsequently played the title role in the film Agent Cody Banks, as well its the sequel, Agent Cody Banks 2: Destination London. The first film opened in March 2003 and grossed $47 million; the sequel, which opened a year later, grossed $23 million. Muniz trained in martial arts for the films, and performed most of his own stunts; he also commented that it was the point in his career where he should "make the transition from child actor to an adult actor or a respectable actor".

Muniz had a cameo in the comedy Stuck on You and voiced a racing zebra, "Stripes", in the 2005 film Racing Stripes. His latest film, the horror movie Stay Alive, opened on March 24, 2006. In April 2006, Muniz will begin filming My Sexiest Year, an independent film which will be shot in New York City and Miami, and which will star Harvey Keitel as Muniz' father. Muniz' character will have a love scene in the film.

Malcolm in the Middle will finish its run in May 2006. Muniz has expressed a desire to leave traditional Hollywood film roles behind, saying that "growing up has never scared me until last year. I started thinking about getting older, being an adult, and it scared me. Hopefully things will work out in my career. If they don't, then it was never meant to be".

In April 2006, Muniz announced he was taking a break from acting to pursue a career in race car driving, saying that "Truthfully, I think it will be easier for me to leave for a while and come back when I'm 23, 24 and be an adult and start fresh".

Personal life Muniz enjoys playing the drums, basketball, as well as golf, having been taught to play by his grandfather at the age of five. He is a close friend of actress Hilary Duff, whom he first met before they both became well-known, as well as musician Zac Hanson, whose band he joined on their Underneath tour in 2004. Muniz has also developed an interest in performance/collector cars and auto racing; he owns a Porsche 356 "Speedster", and won the Toyota Pro/Celebrity Race in 2005.

Muniz, who has been home schooled since the sixth grade, has pushed back his plans to attend college, choosing to concentrate on his acting career. In 2003, he commented that he "hates teenagers", calling them "the most annoying people on the planet", and saying that at the time he had never tried smoking or drinking.

Muniz' first serious girlfriend was Megan, a high-school junior. The two broke up shortly before the release of the first Agent Cody Banks; Muniz has said that she was his "first love, ... first anything". In July 2005, Muniz, who was nineteen years old at the time, proposed to his girlfriend, Jamie Gandy, a local hairdresser who is six years older. The two met on the New Orleans set of his film, Stay Alive. In late 2005, he bought a home in Manhattan; he had previously lived in Brentwood, California and Encino, and plans to move to his fiance's native New Orleans after his wedding in the summer of 2006.