The world number one was only briefly troubled by her ninth-seeded opponent in Cincinnati and won the WTA Premier hard-court event for the first time.
Williams needed just over an hour to win her fifth WTA singles title of the year as she improved her head-to-head record against Ivanovic to 7-1.
Ivanovic rarely looked like adding to her career haul of 14 WTA titles, double-faulting four times in the match and winning just half of her first service points as she was swept aside by the 17-time grand-slam champion.
Williams made a slow start and quickly found herself 3-1 down, after wasting two break points in the fourth game, but recovered well to break and level in the sixth.
The top seed, who saw off Caroline Wozniacki in the semi-final, then took her ace count for the first set to six as she moved ahead in the match.
Avoiding a repeat of her sluggish start in the second set, Williams reeled off the final five games - serving out to seal victory in comfortable fashion.
While Ivanovic saw off Williams in three sets at the Australian Open earlier this year, the world number 11 has now lost to the American three times since that success in Melbourne.