The 26-year-old Wozniacki, who will now move back into the world's top 20, has been in fine form, winning 19 of her last 22 matches, but was pushed to her limits by Mladenovic during an intense two-hour-40-minute final.
Despite a strong start from the Dane, Mladenovic, who underwent lengthy treatment after the opening set, refused to back down as she produced a spirited performance to win the second set, the only one Wozniacki dropped during the tournament.
Wozniacki, who won the Pan Pacific Open last month, held her nerve as she showcased her years of experience to clinch the third set and claim her second Tour title of the year.
"I'm really pleased with my week, there was some good tennis and long battles," Wozniacki told reporters.
Wozniacki said it was difficult psychologically as she did not know the extent of Mladenovic's injury in what became a gruelling match.
"It wasn't easy mentally because sometimes she would look like she couldn't play, and then she would run like Speedy Gonzalez -- clearly it's not that bad if you can run side to side," she added.
"There was definitely a mental game. I just happened to win it."
Mladenovic said she had struggled with exhaustion due to the intense heat and humidity in Hong Kong and sustained a hamstring injury during the final.
"I was not coming out fresh and when you play someone like Caroline, who is running down every point, you have to fight," said Mladenovic, who is yet to win a Tour title following her third loss in a singles' final.
"It was very difficult. I have no idea how I made it to three sets."
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Toby Davis)
