The Hawks won for the 10th time in 12 games, building a 12-point lead heading into the fourth quarter and then holding on against a team that was meeting a division opponent for only the second time this year.
Horford scored 13 points and grabbed 13 rebounds while Josh Smith produced 16 points, 11 boards and five blocks. It was Atlanta's eighth straight victory over the Magic.
Arron Afflalo scored 16 points to pace Orlando, which has dropped three out of four. J.J. Redick added 13 for the Magic.
Orlando's only other game against a Southeast Division foe this season was also against Atlanta. The Hawks won that one by nine on Nov. 19.