The game marked the return to Atlanta for Josh Smith, who played with the Hawks for nine years before signing with the Pistons as a free agent prior to this season.
Millsap missed Tuesday's game against Miami, but was sharp against the Pistons while hitting 8-of-14. DeMarre Carroll, one of the players obtained by Atlanta this year in an attempt to make up for the absence of Smith, scored 11 points and had 12 rebounds.
Brandon Jennings had 21 points and seven rebounds to lead Detroit. Smith, received warmly by the Atlanta crowd, hit just 5-of-15 from the field and scored 11 points.
Atlanta led by only two points heading into the final period, but built as much as a 13-point lead during the quarter.