Ivanovic, who struggled with her serve during an extended two-year slump, finished Sunday's contest with an ace on match point.
"There will be some ups and downs until I get to that level where I feel comfortable playing against top players all the time, but I feel very confident about my game and my fitness," said Ivanovic, who has now won 13 of her last 15 matches.
The former No. 1 also ends the season inside the Top 20 after starting the year ranked No. 21 and falling as low as No. 65 in between.
Kimiko Date took third place in the championships, defeating Daniela Hantuchova 7-5, 7-5 in the semifinal playoffs.