The Spurs put the Lakers away in the fourth quarter en route to their 11th straight win, as Leonard finished with 22 points and 10 rebounds and Duncan added 12 and 16 in the victory.
Los Angeles suffered a 34-point loss to the Spurs last Friday, and while Wednesday's final score appeared to be lopsided, the Lakers stayed close through three quarters in front of the home fans.
The Spurs led by 11 in the first quarter, but Henry sparked LA's turnaround, first hitting a layup that cut the Lakers' deficit to 35-29 at the end of one, then scoring the first four points during an 8-0 run that gave them a 42-40 lead early in the second.
Even though Henry had 19 points by the break, the Lakers still trailed 58-57 at halftime and went into the fourth down by five, 92-87.
It was still a five-point game before San Antonio's 11-5 run stretched the difference back to double digits, 108-97, on Duncan's mid-range jumper at the midway point.
Marco Belinelli answered a Kent Bazemore 3-pointer with one of his own, and the Spurs cruised over the final five minutes.