The 29-year-old, who began the day with a seven shot lead, always seemed to be in control in the rain-affected final round but had a nervous finish when he was met by a late challenge from rookie Bay of Plenty pro Peter Lee.
Geary signed for an even par 70 and a 14-under par total, in the weather affected 54 hole event, to hold off the fast finish from the 19-year-old Lee who carded a superb six-under par 64 in the wet and cold conditions.
Auckland professional Ryan Fox (67) finished alone in third place on 10-under par while Tasman golfer Blair Riordan (66) was a further two shots back and claimed the North Island Stroke Play title as the leading amateur.
But this week was all about Geary. The former Web.Com Tour player had a remarkable tournament in Auckland and in the opening two rounds was in a different class to the rest of the field.
"I am really happy with the win," said Geary. "It was a bit of an anti-climax the way I played the final few holes but the putter was just dead cold all day. I played really solid I just didn't hole anything. It is still great to win."
The former NZ rep got off to a great start this morning. He birdied three of the opening five holes and at that stage was leading by nine shots. It had the makings of a rout.
Heavy rain swept over the course and forced a suspension of play for 1 hour 20 minutes. Geary returned to the course and his momentum was gone as he struggled with the greens that were two paced after being squeegeed.
"I got some momentum early. I was playing great in the bad conditions and then the last nine holes the greens were totally different speeds. It was a bit of a lottery. So that cost me two or three shots at least. It was playing hard for everyone."
The key to Geary's win was his fast start where he shot rounds of 62 and 64, after hitting 35 of 36 greens in regulation, and making only one bogey, to blow away the field.
"They didn't feel like they were that far out of reach, it was comfortably shooting eight and six under and today would have been the same if the putter was behaving. That is where my game is at right now I feel like I am ready to win at the next level. I am pumped."
Geary feels like he is in coming into some of his best form and is excited about his prospects in 2014. He is seeing his coach James Kupa a lot more now that he is based in New Zealand and that is paying huge dividends.
"I haven't had that luxury the last six years as I have been overseas by myself. It will be good this year if we can keep this consistency of ball striking up.
"I am 29, turning 30 this year, so that is when most golfers come to the peak of their career. My mental game is in good shape, my swing is feeling great and my life is pretty balanced right now so it is good to get out there and enjoy playing some good golf."
Geary's fourth title moves him to joint second on the all-time wins list on the Charles Tour alongside New Zealand No.2 Michael Hendry and one behind five-time winner Doug Holloway.
"It is awesome to get my fourth one. I have a bit more time this year and I am hoping to get a few more wins under my belt on the Charles Tour. Winning breeds that belief that you are good enough to win and it helps a huge amount when you go overseas to compete in bigger events. It doesn't matter what level you are at. It breeds confidence."
The event doubles as the North Island Strokeplay Championship which was won by South Island Amateur Blair Riordan who takes his form into this week's New Zealand Amateur Championship at a golf course he knows well, The Nelson Golf Club
Charles Tour: Recreational Services Akarana Open: Final Scores "“ Akarana Golf Club, Auckland:
Men (Par 70):
196 Josh Geary (P) 62 64 70
198 Peter Lee (P) 69 65 64
200 Ryan Fox (P) 67 66 67
202 Blair Riordan* (Takaka) 65 71 66
203 Jared Pender (P) 67 67 69
204 Dominic Barson (P) 69 70 65
205 Richard Lee (P) 70 68 67, Tae Koh (Manukau) 66 69 70
206 Nick Coxon (Narrows) 72 68 66, Oscar Cadenhead (Clearwater) 67 71 68
207 Brad Shilton (P) 70 68 69
208 Leighton James (P) 68 65 75