The veteran forward, 30, told the club's website that the Kangaroos had shown a lot of faith in giving him a new contract.
The decision to stay with North removes Petrie from the list of restricted free agents at the end of the season.
"There will be more movement of players in the coming years with free agency, which is great for players, but that's never entered my mind. As long as the club was happy to do a deal then I was always happy to stay," Petrie told the Herald Sun.
Petrie said the future was bright at Aegis Park.
"While we haven't got the wins on the board, there is a lot more depth of talent now. Benny Jacobs has played a few games this year, Taylor Hine as well, and you've got (Ryan) Bastinac, (Ben) Cunnington, (Jack) Ziebell, all those blokes have continuously built on good seasons last year, so there is definitely potential for some good finals action in the next couple of years and that's why I want to stay around to be a part of it."
He said his body was feeling as good as ever: "I don't want to jinx myself, but apart from 2010, I've only missed one game through injury across 13 years. I missed one game with a rolled ankle in '06.
"Touch wood, I've always been very professional with preparing each week and making sure the body is in good nick. You have got to be more particular now after reaching the big 30. I do enjoy the recovery side of footy and I still love training and getting out there on the track.
"I haven't missed a training session throughout pre-season. I started a fortnight later than the boys and haven't missed a session since joining the boys in Utah."
