Hopes a New Zealand triumph might follow Steve Alker's win in the PGA at Clearwater last week were dashed when the Americans took control of the tournament.
Geary followed his second at the PGA with a tie for fourth, posting 71 in the final round to finish at 12-under-par 276.
"It's really satisfying," the Tauranga 24-year-old said. "It hasn't really sunk in. I'm sure it's going to be a cool feeling."
Geary picked up three shots through the first five holes but then had a double-bogey on the sixth and bogies on eight and nine.
"I had a good start. I was cruising after getting a couple of good breaks.
"Then I hit the water on six and that kind of killed the momentum. I three-putted eight and hit a bad shot on nine.
"I had to guts it out after that. Things just weren't going right at the right times."
Geary confirmed temporary membership status on the Nationwide Tour with his placing and said that was a relief.
He has spent the last two years on the Canadian Tour.
He was joined in Arrowtown by his brother, Brad, and joked he might now have earned enough to take his older sibling to the United States.
"It's pretty slow right now in the building trade, so he might join me."
Geary led the tournament when he got to 14-under through five holes and attracted the biggest galleries, but he said he never felt the pressure of being the home favourite.
He qualified for the British Open last month and played superbly at both Clearwater and The Hills, but he said that was always the plan.
"My expectations were fairly high to be honest because I've been hitting the ball really good.
"I knew it was only a matter of time before I holed a few putts."
Holing putts was a problem yesterday for another New Zealander, Grant Waite, who started the round as co-leader.
Waite blew out with a 76, including six bogies, to tie for 29th on seven-under.
Other New Zealanders to play at the weekend were Alker (tied for 13th on 10-under) Michael Long (tied for 22nd on nine-under) and David Smail (tied for 25th on eight-under).
