McKinnon, who won the national title in Gisborne in January this year, held off a strong challenge from Piha's Floyd Smith to claim the honours.
The pair were tied on points going into the final event of the tour.
Both had one win and a second placing each but McKinnon's victory saw him win the overall title and earn selection in the New Zealand team for the World Surfing Games in Costa Rica next year.
"Yeah, it's cool," McKinnon said.
"I've been doing this for a while, though. I used to compete in the late 90s and went to the world champs in Hawaii in 1999 and 2000. And I just came back from the world champs in Hawaii again in February this year."
Light winds made conditions hard to pick at Chalets Break but the 28-year-old seized the initiative in the final when he capitalised on better waves with some high-scoring moves.
"It was overcast and they [the waves] were quite weak beach-break waves, similar to what you get at St Kilda here but just not very powerful."
Despite the challenges, McKinnon managed a couple of "massive tweaked inverts" - in others words, he cut back up the wave using it as a ramp to jump into the air.
It was an impressive move in the conditions.
"The lip was quite lumpy, so if you were able to do something like that you were going to score highly.
It's got a lot to do with your wave selection as well.
You need to select good waves and only use waves you know are going to be high-scoring."
McKinnon got his start surfing the breaks at Castlecliff Beach in Wanganui as a 16-year-old but has drifted in and out of the sport over the years.
Mt Maunganui's Luke Elliot finished third and Wellington's Richard McKenna was fourth.
