The 32-year-old, who joined Quins from Otago in 2008, has made 106 appearances for Quins, scoring 1,184 points and bagging 16 tries.
Evans, who represented the All Blacks at the 2007 World Cup, says he is relishing the chance to establish Quins as a dominant force both domestically and in Europe.
“My decision was made easy by the ambition of this great club, the success we have had and the hunger to want more,” Evans said.
“The support I have had from the supporters has been amazing and I will do my best to help the club stay one of the major forces in English and European rugby.”
Harlequins director of rugby Conor O’Shea added: “There is not a player, supporter or coach in the game in England, let alone Harlequins, who will not be delighted that Nick Evans has agreed to stay with us for another three years.
“The Aviva Premiership wants the best players playing in it and Nick is one of the very best. He contributes so much to this club both on and off the field and is the perfect role model for all young players.
“While I know one of the main reasons he is staying with us revolves around his family, ultimately it is about his ambition to achieve things with this club. We have started something here and Nick wants to see it through. His decision to stay is a great early Christmas present for all Harlequins supporters!”