The kidnapping took place on the sparsely populated Great Barrier island when Nortessa Montgomeri, a 20-year-old student, was sleeping beside her partner Thursday night.
She was rescued 36 hours later after the alert boy, Callum Grady, heard the victim calling for help and immediately informed his mother, who in turn called police, the New Zealand Herald reported Sunday.
Montgomerie's former boyfriend, Nathan Boulter, 21, is alleged to have abducted her. He has been arrested.
Detective Inspector Scott Beard said Montgomeri was "quite traumatised".
Montgomerie's grandfather, Tony Powell, said she had an unhappy relation with Boulter.