Williams, 29, got off to a slow start, trailing the 19-year-old Wozniacki 3-1 before a series of aces and blistering groundstrokes helped her pull ahead, winning the set 6-4.
Williams, a seven time Grand Slam winner, said she was happy with her performance against the Dane, who is ranked fourth in the world.
“I felt pretty good playing against such a competitive player,” Williams told reporters.
“She plays so well.”
The American struggled for much of 2009, losing her Wimbledon crown to sister Serena and then crashing out of the Beijing Open in October.
Earlier Thursday, Belarussian Victoria Azarenka, 20, beat Argentine Gisela Dulko, 24, by a 6-1 margin.
The Hong Kong tournament features four teams with three players each — representing Russia, Europe, the Americas and Asia Pacific — in singles and mixed doubles play. The tournament wraps up Saturday.
On Wednesday, former world number one Russian Maria Sharapova pulled off a comeback win against China’s Zheng Jie 6-7, 6-4, 6-2, while Russia’s Vera Zvonareva easily overpowered Japanese newcomer Ayumi Morita, beating her 6-2, 6-2 in just over an hour.