The NBC singing show announced that Williams will rotate in for season seven, following Green's exit last month, said the Hollywood Reporter.
"It's been a huge year for Pharrell, with recognition for his contribution in the world of music -- the Despicable Me franchise soundtracks, his Oscar-nominated song 'Happy' and his Grammy-winning collaboration with Daft Punk on the breakout dance hit 'Get Lucky'.
"His dominance in record sales in 2014, coupled with his incomparable accomplishments in the world of fashion and design, make him an irresistible addition to The Voice family," said Paul Telegdy, president of alternative and late night programming for NBC Entertainment.
Williams previously served as a guest mentor to Usher and his team during season four.
Green had recently announced that he is parting ways from the talent show to focus on his own musical career.