Having spent the last six years with Quins, the 25-year-old has revealed that the club's recent success meant that he never had any intention of leaving the Stoop.
"There is no other club that I want to play for so I'm pleased to extend my contract with Harlequins," he told the club's official website. "I'm enjoying being part of a talented squad that is playing an attractive and successful style of rugby.
"Winning trophies is why we play professional rugby and having tasted some success in that regard, I would like more.
"I believe that the best is yet to come from our players which is why I'm looking forward to another three seasons with the club."
Care has made 33 appearances for the English national team.