A successful 2008/09 season saw the back row receive the prestigious title of English Premiership Player of the season, along with his first International cap in the summer tour of 2009.
"Harlequins are a great club and one which I think is on the verge of great things in the coming years," he said.
"We have a squad with a great mix of youth and experience and we are trying to play a brand of rugby that will excite and challenge. I believe that through Harlequins a number of us can achieve our aims of playing for a winning club at the highest level whilst also pursuing our dreams of playing for our country.
"It is a real honour to be captain of one of the oldest rugby clubs in the world and certainly one of the most recognisable and in the short term I can't wait to lead the boys out on Friday in the Amlin Challenge Final, which will be our first major final since 2004."