"I'm disappointed to have to withdraw from the Pan Pacific Open, which I was very much looking forward to playing this year," the American was quoted as saying.
"Unfortunately with the number of matches I have played throughout the summer I need more time to properly recover."
Williams, who won her fifth US Open singles title this month, was the latest high-profile withdrawal from the September 22-28 tournament after Russian Maria Sharapova also pulled out last week to recover from a right shoulder injury.