The full-back, who progressed through the Barnsley FC Academy, will now remain a Red until 30th June, 2016.
The 18-year-old signed his first professional deal last June and has made six appearances for the first-team since recovering from a fractured toe sustained in July.
Speaking after signing his new deal, Smith said, “I’m over the moon to extend my stay here. I was obviously disappointed suffering the injury in pre-season but I feel that I’ve come back stronger and I’m determined to keep on improving.”
