In what was a mere formality, Serena was presented with the award during an on-court ceremony at the NASDAQ-100 Open in Miami.
Slovak Daniela Hantuchova scooped the Most Improved Player award.
Her record for the season was 56-5 -- 17-2 against the top-10 opponents.
Hantuchova won the Most Improved Player award after starting the year ranked 38th and rocketing to eighth in the world.
She won the prestigious Pacific Life Open in Indian Wells, reached the Wimbledon and US Open quarter-finals and led her country to its first-ever Fed Cup title.
The WTA Tour's annual awards are voted by players and the media.