Riegger completed his first tour title at 17-under-par 271. He also collected the second biggest first-place check of the year - $135,000.
'I knew going into the day what playing good today would mean,' said Riegger, who jumped to sixth on the Nationwide Tour's money list. 'I wasn't feeling my best, but I managed to get the job done and that's all that matters.'
The win came despite a bad back that bothered him all week.
'I'm going home tonight and I'm going to get a shot in my back,' Riegger admitted. 'I've been down on the back all week. It didn't look like it the way I played, but I was in a lot of pain out there all week.'
B.J. Staten was the only player to post four rounds in the 60s this week, but it wasn't enough. He also closed with a 68 to end one back at minus-16. Roland Thatcher and Kris Blanks shared third place at 15-under-par 273.
Tag Ridings, who shared the lead after three rounds with Riegger and Jason Day, carded a 1-under 71 Sunday to end alongside Jay Williamson in fifth at minus-14.
Staten and Riegger were just two of several players atop a crowded leaderboard on this day. Staten moved out in front early. He birdied the first two holes before tripping to a bogey on three.
The 28-year-old Staten bounced right back with a birdie on the fourth. He got to 15 under with a birdie on the par-4 sixth. However, he ran off 10 straight pars from there as others came into the picture.
Riegger was playing in the final threesome. He dropped a shot at the third to slip to minus-12, but bounced back with three birdies over the next four holes.
The 43-year-old Riegger remained at 15 under with four straight pars. He dropped another stroke on the 12th, but recovered in style once again.
Riegger rolled in a 9-foot birdie putt on 13 and followed with another birdie on 14, from 6 feet out, to get to 16 under. As he parred the next three holes, Staten joined Riegger in the lead with a birdie on the par-3 17th.
Staten had a chance to grab first by himself, but parred the par-5 18th at The Glen Club to finish at 16 under.
Riegger headed to the last needing birdie or eagle to grab the title. He drained a 18-foot birdie on the 18th for the win.
Thatcher, playing alongside Staten, got to 16 under with four front-nine birdies, but posted eight pars and a bogey on the back nine to end two back.
Chris Smith (67) and Livermore Valley Wine Championship winner Omar Uresti (71) ended in a tie for seventh at 13-under-par 275.
The 19-year-old Day struggled to a closing 73. That dropped him into a share of ninth at minus-12. He was joined there by Rich Barcelo, Jeff Klauk, James Driscoll, Michael Long, Tee McCabe, Dustin Bray, Chris Stroud and Bob Burns.