Geary (34), from Mount Maunganui, had started the day one shot behind leader Zach Murray and in an up-and-down round ended up finishing tied for second with Australian Ashley Hall, two shots behind Murray.
Geary birdied the first two holes but then had three bogeys on the front nine and at one stage he was five shots behind the lead.
But he dragged himself back into contention, including an eagle on the 13th, which was almost an albatross. He ended up shooting a three-under 69.
Geary said he was always chasing the win hard.
"It was a shame I lost momentum on the fifth hole and that sort of started a weird set of holes. I bounced back pretty well from that but it was too little, too late," Geary said.
"Going into today I knew it was not going to be a two-way match, there would be some low scores in behind. But no-one really shot the lights out in front of us so it did became a bit of a two-horse race."
He paid tribute to winner Zach Murray, who he said played very solid golf.
He said wanting to be a New Zealander winning the 100th NZ Open was on his mind.
"Absolutely [there was pressure]. But in a good way. I had a lot of support out there, from the crowd, family and friends, It would have been nice to finish it off but there are encouraging signs for the future."
Steven Alker had a seven-under round yesterday and surged up the leaderboard, eventually finishing on 16 under and a share of eighth.
Alker said afterwards he had sunk a few putts early on and from there just got some momentum into his game.
"I struck it well all week and gave myself lots of chances so I think the difference today was the putting. I only made two bogeys for the whole week so not a lot of birdies for the first three days," he said.
His experience of playing on the Web.com tour in the United States helped on The Hills course.
"You have to hit the ball high and put a bit of shape on it. I just enjoy coming here and play. The scenery is so great and I can relax a bit and enjoy the week."
He never honestly thought he could catch the leaders, starting eight shots off the lead.
"I never looked at the leaderboards today. I think I was too far back. If I could have snuck in a 61 or 62 I might have had a chance."
Harry Bateman finished up on the same score as Alker.
Ryan Fox started well in his final round and did not hit a bogey all round, hitting a five-under 67.
But with plenty in front of him, he ended up on 15 under for the tournament.
Queenstown golfers Ben Campbell and James Anstiss both finished with respectable rounds yesterday.
Campbell finished on nine under, after an impressive final-round 67 at The Hills. He ended tied for 33rd while Anstiss was one shot back with a 69 yesterday. It was the first time at the Open for Anstiss, so to make the cut and finish inside the top 40 was a good effort.
