The 36-year-old Whittaker, a playoff loser last week in Texas in the WNB Golf Classic, had a 17-under 271 total on the Black Creek Club course.
'I knew I was going to win. It was just a matter of time,' Whittaker said. 'I've been playing really well.'
Whittaker, the former Wake Forest player who has made 12 trips to the Q-school finals, earned $85,000 to jump from 27th to 11th on the money list with $254,900. The top 25 after the final two events will earn 2008 PGA TOUR cards.
'By winning this tournament, the result is getting my card,' he said. 'It's special, because I beat a bunch of guys out here. I'm now known as a winner here in Chattanooga, my favorite place in Tennessee.'
McKenzie finished with a 68. He earned $51,300 to more from 43rd to 24th on the money list with $179,178.
'I played nicely this week without having my best game,' he said. 'I'd rather have my `A' game and finish 20th. But I'll take where I finish and be quite happy with it.'
Tag Ridings (68), Tommy Tolles (68) and Patrick Sheehan (69) tied for third at 15 under, and Brad Elder (69) and Henrik Bjornstad (72) followed at 14 under.
After bogeying the 17th, Whittaker played the par-5 18th conservatively, laying up to 80 yards and two-putting for par from about 8 feet.
'You don't realize how hard an 80-yard shot is to win a tournament,' he said.