'This feels amazing,' said Tambellini, who picks up $108,000 with the win. 'To finally be able to do this for my family, hometown and all of those who have supported me is fantastic.'
Tripp Isenhour, who won the Charity Pro-Am at The Cliffs earlier this year, carded a 7-under 64 to move to 11-under-par 273. He was joined there by Charles Warren, who closed with a 1-under 70. John Paul Curley, Ryan Palmer, Jeff Quinney and Tjaart van der Walt finished one stroke further back at minus-10.
Tambellini, who led by four entering the round, quickly extended that lead with back-to-back birdies from the second at Hillcrest Country Club. His lead continued to grow when he rolled in a 35-foot birdie putt at the sixth.
However, the wheels started to fall off a little from there. The 28-year-old dropped shots at the seventh and ninth to make the turn at 15 under. He later bogeyed the 13th to fall to 14 under and his lead was just two.
The Californian caught fire from there. He sank back-to-back birdies from the 15th and rolled in another birdie, from 12 feet out, at the last for the six-shot win.
'It has not sunk in yet,' said Tambellini. 'But then again I don't know what it is like for a win out here to sink in. Winning a Nationwide Tour event is a big deal.'
The win also moved Tambellini closer to his ultimate goal of playing on the PGA Tour. He needs to finish in the top 20 on the Nationwide Tour money list to gain his PGA card for next year.
'It is always in the back of your mind to get your PGA Tour card,' said Tambellini, who moved to 18th on the Nationwide Tour money list with the win. 'It is the ultimate goal of every guy out here to finish in the top 20 and play on the PGA Tour. But to actually get close to reaching your goal is unbelievable.'
Isenhour mixed two birdies and two bogeys over his first nine holes. His second birdie was on the ninth and that set him on a tear. Around the turn, he birdied the 10th, 11th and 12th to get to 7 under.
After dropping a shot at the par-3 13th, Isenhour ripped off five straight birdies to close out his round.
'That was fun,' Isenhour said. 'I just kept focusing on hitting good shots. Nine birdies in 10 holes, I don't think I've ever done that.'
Warren, who trailed by four entering the final round, parred his first 10 holes. He finally got on the board with a birdie at No. 11. His birdie on the 14th got him to minus-12, within two strokes of Tambellini.
However, Warren stumbled to two straight bogeys before birdieing the 17th for a share of second.