Williams, who cut her foot on broken glass at a restaurant after winning Wimbledon this year, returned to practice earlier this month.
Williams headed a strong field for the Sept. 26-Oct. 2 Pan Pacific Open. Wimbledon runner-up Vera Zvonareva, French Open champion Francesca Schiavone, Caroline Wozniacki and Jelena Jankovic have also entered the tournament. Maria Sharapova returns to defend her title.
After missing this year's U.S. Open, Williams told The Associated Press on Sept. 13 she was yet to decide when she'd return to competition, but plans to play for the United States in the Fed Cup final against Italy in November.