The two big movers up the rankings this year stood toe to toe for three hours at the Khalifa Tennis Centre before Azarenka went into meltdown late in the third set after squandering two match points in their White Group clash.
World number four Wozniacki was outplayed in the first set, but the U.S. Open runner-up gradually found her range, breaking twice in a 79-minute second set to take it to a decider.
After a 10-minute heat break enforced because of temperatures still hovering in the low 30s Celsius despite darkness having long fallen over the Qatari capital, Azarenka again took command, moving into a 5-3 lead.
However, Wozniacki broke back and then saved two match points to cling on to her own serve, prompting the Belarussian to smash two racket frames in frustration.
Wozniacki seized her opportunity with relish, breaking Azarenka's serve again before serving out for victory that puts her level on one win with Azarenka who marked her debut on Tuesday with a straight sets defeat of Jelena Jankovic.
(Reporting by Martyn Herman; Editing by Sonia Oxley; To query or comment on this story email sportsfeedback@thomsonreuters.com)
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Caroline Wozniacki reminds me of Steffi Graf, and, is, for sure, going to be around for a long time to come. She conquers not only her opponents but the spectators also. Her words touch the heart. What she said after defeating Melanie Oudin at the US Open was an example. I am a staunch supporter of Kim Clijsters, but was in an unusual dilemma while watching the US Open final between Clijsters and Wozniacki: I wanted both to win! At the end, I was happy Clijsters won, but sad Wozniacki didn’t!