Maguire's first appearance in a feature film was in the 1989 movie The Wizard. In that movie, he played a goon of Lucas Barton, one of three competitors at a video game competition, and had no lines. Maguire initially worked as a child actor in the early 1990s, often playing roles much younger than his chronological age; as late as 2002, Maguire was still playing teenagers while in his mid-20s. He appeared in a variety of commercials and TV and movie roles, working opposite such stars as Chuck Norris (Walker, Texas Ranger), Roseanne Barr (Roseanne), and Tracey Ullman (Tracey Takes On...). Eventually, Maguire was cast as the lead in the FOX TV series Great Scott, which was cancelled 5 weeks later.

During many of his auditions, Maguire found himself competing opposite another rising child star actor, Leonardo DiCaprio. The pair struck up a fast friendship and made an informal pact to help each other get parts in their movies/TV shows/other projects. For example, both auditioned