Smith's first acting job was at the age of 14 months in a Tide television commercial. His first leading role was in Leapin' Leprechauns in 1995, and later movie roles included Harriet the Spy opposite Michelle Trachtenberg and Rosie O'Donnell, Small Soldiers opposite Kirsten Dunst and Phil Hartman, Krippendorf's Tribe, The Patriot opposite Mel Gibson, Heath Ledger and Joely Richardson and American Outlaws opposite Ali Larter and Colin Farrell. Smith also appeared on Zenon: Girl of the 21st Century opposite Kirsten Storms and Raven Symone, Kate Brasher opposite Mary Stuart Masterson and Rhea Perlman, and the TV miniseries A Wrinkle in Time opposite Katie Stuart.

Smith is probably best known for his role of 'Ephram Brown' on Everwood. Like his character on the show, Smith is Jewish in real life.