Thomas Dekker first appeared as a child actor in the mid-'90s, with a couple of television guest appearances, and then a small role in Star Trek Generations, playing Thomas Picard, the son of Captain Jean-Luc Picard in an alternate timeline. At the age of seven, he toke on a more elaborate part, playing one of the homicidal, otherworldly tykes in John Carpenter's sci-fi horror remake Village of the Damned (1995). After a couple of appearances that same year as Henry on Star Trek: Voyager, and assignments voicing anthropomorphic mouse Fievel in two direct-to-video American Tail sequels, Dekker played Nick, one of the Szalinski kids, on the TV series version of Honey, I Shrunk the Kids, which ran for three seasons. He also portrayed the young pop star Donny Osmond in the 2001 telemovie Inside the Osmonds.
In the ensuing years, Dekker continued to primarily work in television, in guest roles on such popular series as Boston Public and House. He also took on a recurring part in 2005 as Vincent on the long-running family drama 7th Heaven, but he didn't truly break through to major success until he was cast on the soon-to-be major hit show Heroes in 2006. Though Dekker only played the unlikely friend of indestructable cheerleader Claire Bennet, the exposure helped earn him one of his biggest roles yet, that of young hero-to-be John Connor on the heavily promoted sci-fi film-to-TV adaptation Terminator: The Sarah Connor Chronicles (premiering in 2008).
Over the following years, Dekker would continue to act in movies like My Sister's Keeper and on shows like The Secret Circle.