Thomas began appearing in screen roles in the mid 1990s, and had minor roles in several films, including Conspiracy Theory (1997), Can't Hardly Wait (1998) and Cruel Intentions (1999). His first leading role was in the teen romance Save the Last Dance, in which he starred opposite Julia Stiles. The film opened in January 2001 and became successful among teen audiences, grossing over $90 million domestically. Subsequently, Thomas appeared in supporting roles in the films Barbershop and Halloween: Resurrection, both of which were released in 2002. Thomas was a cast member on The District, a television crime drama that aired on CBS from 2000 to 2004.