A layup by Michael Kidd-Gilchrist put the Bobcats in front 98-92 with 3:58 to play, but they did not score another point. Charlotte missed three shots and turned the ball over three times the rest of the way.
Smith came through with the last of his 13 points off the bench to bring New York its fourth consecutive victory. Charlotte has lost five in a row.
Charlotte outrebounded New York by 14, but the Knicks turned the ball over just eight times and made 13 shots from 3-point range.
The Bobcats were led by 25 points from Kemba Walker and 18 from Gerald Henderson.