Horford was the third overall pick in the draft after helping Florida win consecutive NCAA titles.
The game tipped off at 10:30 a.m. for the Bobcats' annual "Cool School Field Trip," and the stands were packed with area eighth graders who earned an invitation by posting good grades and no absences since the start of the school year.
Josh Childress added 19 points for Atlanta, Josh Smith had 17, Marvin Williams 12 and Anthony Johnson and rookie Acie Law 10 each.
Gerald Wallace had 34 points and 10 rebounds for the Bobcats, who were out rebounded 45-29 -- including 17-4 in offensive boards. Jason Richardson had 17 points and Raymond Felton added 13.
Down nine at halftime, Charlotte led three times in the third quarter, the last at 62-61 on a pair of free throws by Wallace with 3:15 left in the period.
The Bobcats tied it at 76 on a layup by Richardson with 10:35 remaining in the fourth quarter, but a jumper by Williams followed by Horford's dunk put Atlanta ahead to stay.
Atlanta center Zaza Pachulia left late in the third quarter after spraining his left knee.