John Rollins (66), Rod Pampling (67), Jim Benepe (68) and Billy Judah (70), who shared the overnight lead with Long, finished tied for third at 12-under-par.
Long reached the putting surface at the long, par-5 2nd hole and watched as the ball rolled six feet from the cup. He two-putted for the birdie and added a seven-foot birdie at the next hole, also a par-5.
The 33-year-old rolled home another seven-foot birdie try, this time at the fifth. He added a birdie at No. 7 and went on to par the next five holes before bogeying the par-3 13th.
That was enough for Long to hold on for the victory. Van der Walt made back-to-back bogeys at 12 and 13 but one birdie over his last five holes was not enough to catch Long.
'I'm blown away at the moment,' said Long, who earned $100,080 for his first win on the Buy.Com Tour. 'It really is an amazing feeling.'
A year ago, Long was involved in a surfing accident that broke a bone in his neck, close to a bone that could have caused paralysis.
'Last year was a disastrous year,' he said. 'This year I've come back a lot stronger. This is turning out to be a pretty good year.'
Van der Walt posted a three-under 68 on Sunday for his highest finish of the season. The 26-year-old might be in the middle of his finest stretch of golf this season as he took a joint fourth two weeks ago at the Tri-Cities Open.