Imada three-putted for bogey on the first extra hole, while Gow was unable to get up-and-down for his par at the par-3 11th. Both players then two-putted for par at the par-4 12th.
They moved to the par-5 13th at the Cliffs Valley Course where Imada had a chance to win, but he was unable to sink his birdie putt. Gow meanwhile saved par from a greenside bunker.
Imada dropped his tee shot some 12 feet from the cup on the 11th, which was the fourth extra hole. Gow found a hazard off the tee, but managed to play out of it and save par. Imada missed his birdie putt and it was back to the 12th.
After both men found the fairway off the tee, Imada stiffed his second shot within three feet of the cup. Gow was not much worse off as he knocked his second shot to 15 feet.
Gow missed his birdie try setting the stage for Imada. The 2000 Virginia Beach Open winner calmly sank his birdie putt for his second Nationwide Tour crown.
'It wasn't a surprise, but it was great to see that ball go in the hole,' said Imada, who earned $108,000 for the win. 'It feels like forever since the last win. I didn't know how hard it was to win on this tour.'
Jason Gore and Bryant Odom posted matching rounds of 5-under 67 to finish at 16-under-par 271. They were joined in a tie for third by Rick Price (69), Shane Bertsch (68) and Richie Coughlan (68). Jeff Klauk and third round co-leader Kyle Thompson finished one stroke further back at minus-15.
Gow started his day three shots behind Imada and Thompson and began with a birdie at the second, but stumbled to a bogey at the very next hole. He came back to birdie Nos. 5, 7 and 9 to get to minus-14.
Around the turn, Gow dropped in a birdie putt at the par-4 12th. He jumped into the lead at 17 under as he closed with back-to-back birdies from the 17th, including a 30-footer at the last.
'I made birdie on the last two holes and then just had to hang on and wait,' said Gow, who lost the 2002 B.C. Open in a playoff to Jeff Sluman.
Imada quickly jumped out in front with birdies at the first and third. However, he faltered to a bogey at the fourth but erased that mistake with a birdie at the par-5 sixth.
The 27-year-old Imada dropped another stroke when he bogeyed the par-4 eighth. He came right back with a birdie at the next to return to minus-16.
Imada tallied another birdie at the par-4 12th to get to 17 under. After five straight pars, he had a chance to win it at the last, but missed a 7-foot birdie try to create the extra session.
'The miss on No. 18 was the easiest putt you could have,' said Imada. 'It was to win and I tensed up a little bit.'
Darron Stiles fired a 6-under 66 to finish at 14-under-par 273. He was joined in a tie for 10th by Anthony Painter, Sonny Skinner, Steven Alker, Brad Bryant, Tony Carolan and Vance Veazey.
Jody Bellflower and Tyler Williamson both closed with 69s to end one stroke further back at minus-13.