The Pacers (6-3) were led by Roy Hibbert with 19 points and David West with 15.
The Sixers entered the game surrendering a league-low 85.6 points per game and holding their foes to a league-low 39.5 shooting percentage. The Pacers, seeded eighth last year right behind the Sixers, have been almost as stingy, ranking third in the league in points allowed (89.3) and shooting percentage (41).
Early on, the Sixers' defense made the difference.
Indiana reserve guard Lance Stephenson's jumper with 56 seconds to play in the first quarter pulled the teams even, 20-20.
However, the Sixers held the Pacers scoreless until the 9-minute, 47-second mark of the second quarter. During that stretch, the Sixers ran off 11 consecutive points, capping the run with Williams' 17-foot jumper for a 31-20 advantage with 10:11 remaining in the half.
But unlike some of the Sixers' other victims in this young season, the Pacers didn't tuck their tails and give in. They responded with a run of their own. Nine straight Pacers points, capped by a Tyler Hansbrough jumper with 5:56 to play, pulled the Pacers to within 31-29.
But the Sixers, who trailed by five points in the first quarter, did not surrender their lead in the second.
Hawes, who was playing with a stiff lower back, responded with a short jumper. Iguodala followed with a three-pointer, and the lead was 36-31.
Although the Pacers cut their deficit to two points later in the half, that was as close as they got as the Sixers took a 45-40 lead into intermission.
While Iguodala had 12 points at halftime, the rest of the starters contributed a combined 11 points. This forced coach Doug Collins to turn to his bench, which delivered.
Williams and rookie center Nikola Vucevic both scored eight points, and Vucevic mixed in six rebounds in his 11 minutes.
The Sixers played with significantly more energy in the third quarter, particularly during a stretch midway through the period.
Leading by 54-51, the Sixers outscored the Pacers, 15-3, over the next four minutes to extend their lead to 69-54 with 4:37 left in the quarter, which ended with the Sixers leading by 73-64.
The Sixers have had an interesting spate of games in which they have faced shorthanded teams, and Monday's was no different.
This time, the absent player was Indiana's leading scorer, Danny Granger, who was averaging a team-high 14.9 points. Granger missed the game because of food poisoning.
Contact staff writer John N. Mitchell at firstname.lastname@example.org. Follow him on Twitter @deepsixer3