Williams also received the award for 2002. She won the U.S. Open in September and ended last year ranked No. 1.
Dinara Safina was selected most improved player for 2008, and Zheng Jie was chosen comeback player of the year. Top-ranked Cara Black and Liezel Huber were chosen doubles team of the year for the second time.
Caroline Wozniacki was selected newcomer of the year. Ana Ivanovic was chosen humanitarian of the year for her work and contributions to UNICEF, and Elena Dementieva was honored with the Karen Krantzcke sportsmanship award.
Williams was the only winner not to attend a ceremony Thursday at the Sony Ericsson Open to honor the award winners. She released a statement through the WTA Tour.
"Winning the player of the year award for the second time in my career is a great personal achievement,'' Williams said. "I feel great about my game and hope to win many more player of the year titles in the years to come.''
