Walker, who won for the third time on the Nationwide Tour, completed the event at 15-under-par 273.
'You just have to go out and play as solid as you can and hope for the best,' said Walker. 'You hate to see a guy come back like that, but I wanted to play solid and make some birdies. I did a pretty good job of not giving anything back.'
Justin Hicks (66) and Matthew Jones (68) shared second place at minus-14.
McLachlin led by seven entering the round, but a 5-over-par front nine dropped him as many as four shots behind Walker during the final round. McLachlin closed with a 5-over 77 to join Tom Carter in a tie for fourth place at minus-12.
'It was just a mindset and a game plan. I played a little bit defensively today,' admitted McLachlin. 'My game plan all week was pedal to the metal and to attack the golf course. I made a few defensive swings that hurt. Once I got to a point on the eighth hole it was about even and my competitive juices started kicking in and I played really good after that.'
The 28-year-old McLachlin tripped to a bogey on the third, while Walker birdied the same hole to get within five. That lead disappeared completely over the next five holes at Pete Dye Golf Club.
McLachlin bogeyed the fifth, then Walker birdied No. 6. The seventh saw another two-stroke swing with Walker converting 20-foot birdie putt and McLachlin faltering to a bogey after failing to hit the green in two.
At the par-4 eighth, Walker took over the lead with a 12-foot birdie putt that moved him to 14 under.
McLachlin missed the green short and left at the same hole, then duffed a chip that rolled right back to his feet. He knocked his fourth to 3 feet, but his bogey putt horse-shoed the hole and he walked off with double-bogey and now trailed by one.
Around the turn, Walker converted a 12-foot birdie try while McLachlin three-putted for bogey. That completed a 10-stroke turnaround between the two.
Walker knocked his approach over the green at the 15th. He was unable to get up and down for par and the bogey dropped him to minus-14 and into a tie for the lead with Hicks and Jones.
McLachlin recouped two strokes with an eagle at the 17th, but Walker also made some noise on the par-5. Walker chipped to 5 feet and drained the birdie try to regain the lead at minus-15.
Walker made things interesting at the last. He again knocked his second over the green, but chipped to 5 feet. Walker calmly sank the putt for his third tour title.
'You know '04 happened so fast, then having the injury did make me lose some confidence,' stated Walker, who was the 2004 Player of the Year with two wins that season. 'I worked really hard to get back to where I felt like I was playing really good golf. I felt I was nine holes short all year, I just didn't have a bad nine holes this week.'
Hicks collected five birdies between the third and 11th to jump to 13 under. He dropped a stroke on 13, but birdied the final two holes to finish one back.
Jones ran off three straight birdies from the sixth, but a bogey at the 10th left him at 12 under. He picked up birdies on 12 and 17 to share second.
'I played well today. I had one three-putt, other than that I hit the ball very well,' said Jones. 'I shot a couple less than I probably wanted, but I'm happy.'
Scott Gutschewski posted a four-under 68 to end in sixth at 11-under-par 277. Tommy Tolles, Lee Williams, Ian Leggatt, Scott Parel and Kyle Thompson were one stroke back at minus-10.