Mechlowicz was born in New York City, the son of Susan, a respiratory therapist, and Morris Mechlowicz. He was raised in a tight-knit Jewish family. He grew up in Plano, Texas, where he graduated from Plano Senior High School in 1999 and attended the University of Texas at Austin for one semester. He subsequently moved to Los Angeles, California, where he studied at UCLA and graduated in 2003, with honors, from the Conservatory Acting Programs.

After appearing in a 2003 short film, Neverland, Mechlowicz made his film debut in the raunchy teen comedy, Eurotrip, which opened on February 20, 2004 and received mixed reviews. The same year, he also starred in the independent film, Mean Creek, which was filmed in 2003 but not given a limited theatrical release until August 20, 2004. In the film, which was a dark teenage drama, Mechlowicz played the oldest of a group of teenagers. The film received a positive critical reception. Mechlowicz also received an Independent Spirit Award for his acting in Mean Creek. In 2004 he made a small appearance in the video for Gavin Degraw's hit song "I don't want to be", in which he plays the random football player in the corner. In 2005, Mechlowicz made a guest appearance in an episode of the television series House.

Mechlowicz' most recent role was in the drama Peaceful Warrior (based on the book Way of the Peaceful Warrior), in which he plays the lead role of Dan Millman, an athlete based on the book's author. His next film was the thriller Gone, filmed in 2005 and released in 2007.