Runner-up at this event seven years ago, Ivanovic will get a second chance to claim the title after she got the better of Angelique Kerber in Tokyo.
Top seed for the WTA Premier hard-court event, Kerber was gunning for her second successive final after defeat to Petra Kvitova 12 months ago, but she fell short this time as Ivanovic prevailed 7-5 6-3.
Kerber served for the first set at 5-4 up, but Ivanovic hit back hard, taking all of the next three games to claim the lead for herself.
The crucial break in the second arrived in game four, with Ivanovic going on to clinch victory having won 72 per cent of points on her first serve, compared to just 46 for the German.
Ivanovic will now face second seed Wozniacki, who overcame Garbine Muguruza 6-4 2-6 6-2.
The Dane took the initiative with a break in game 10 of the opening set, only for her unseeded opponent to hit back and force a decider.
Things began badly for the Serb in the final set when she fell behind to an early, but from 2-0 down she reeled off six consecutive games to wrap up victory in a match which lasted over two and a half hours.
Champion here four years ago, Wozniacki will be out for a second title in five years come the final on Sunday.