David West scored a game-high 29 points for the Pacers, who had won four straight and seven of eight.
With Josh Smith, Atlanta's leading scorer this season, unable to play because of a right hip flexor, Hawks coach Larry Drew started Zaza Pachulia, who responded with 17 points and a game-high 14 rebounds.
Indiana never got closer than three in the fourth quarter after Paul George's three-point play made it 91-88 at the 5:18 mark.
Jeff Teague's floating runner made it 101-90 less than 3 minutes later.
George finished with 18 points and George Hill added 15 for Indiana. Hill started and played 33 minutes despite a sore right groin.
Kyle Korver scored five points in a single possession late in the third to push the lead to 12 points.
After officials watched a video replay, the call was upheld that Lance Stephenson committed a flagrant foul on Korver, pushing him to the floor on a play away from the ball. Korver hit both free throws and then a 3-pointer at the 4:10 mark to make it 77-65.
The Hawks' lead swelled to 18 with 2:12 remaining in the third on Ivan Johnson's putback.
Injuries to reserve guards Devin Harris and Anthony Morrow left Atlanta coach Larry Drew with just nine players in his rotation.
Horford, who played 37 minutes despite a right hip contusion, hit a 17-footer to make it 93-88 with 5:02 remaining.
Indiana never led after Korver's 3-pointer made it 18-16 at the 4:13 mark of the first.
NOTES: Smith was injured in Friday's win at Cleveland. Drew listed his status as day to day. ... Hawks rookie John Jenkins scored a career-high 10 points ... Stephenson was helped off the floor with an undisclosed injury with 5:44 remaining. ... Atlanta has won 11 straight at home over Indiana and four straight overall. ... Harris missed his six straight games with a sore left foot. ... Morrow is recovering from a strained right hip after getting hurt at Cleveland. ... Pacers reserve G Sam Young did not travel with the team because of the flu.