Chatwin began his carrer in 2001, at the age of 19, his film debut being in the musical comedy Josie and the Pussycats. After that, he had guest appearances in television series such as Smallville, Just Cause, Glory Days, and Mysterious Ways. He had supporting roles in the films Taking Lives and Superbabies: Baby Geniuses 2. Chatwin gained recognition in 2004 for his role as Tyler McKay in the miniseries Traffic. Next, he portrayed Tom Cruise's son in the blockbuster War of the Worlds, directed by Steven Spielberg. Also in 2005, he appeared in the independent black comedy The Chumscrubber, alongside Camilla Belle, Jamie Bell and Carrie-Anne Moss. In the same year, he played the son of Kevin Nealon's character in the Showtime comedy series Weeds, appearing only in the pilot episode and the series finale. The following year he had a guest appearance in the ABC drama series Lost, and starred in the play Dark Matters in New York.