The 11th-seeded Radwanska defeated Petkovic 7-5, 0-6 6-4 in a match that took more than 2 1/2 hours. The seesaw battle saw 15 service breaks in 28 games.
One of those came in the 12th game and gave Radwanska the first set. After getting swept in the second set when Petkovic won three-quarters of the points, Radwanska came back with three more breaks in the third set in improving to 5-0 lifetime against Petkovic.
It was her seventh career WTA title and comes a week after she won the title in Tokyo. She also won at Carlsbad, Calif., in August. Radwanska, who will return to the women's Top 10 when the rankings are updated Monday, has won 22 of her last 25 matches.
Petkovic fell to 2-3 lifetime in tournament finals.
Radwanska picks up $775,000 along with the title. Petkovic, who was seeded ninth in Beijing, took the runner-up check of $387,750.