The Australian turns 51 this week but announced mid-tournament his plans to step away from competitive golf at the end of the year.
He nearly did it with a bang, joint leader after the first round in Pennsylvania, before settling for third place behind Padraig Harrington.
The Irishman almost surrendered his five-shot lead late in his final round before he holed a 30-foot birdie putt on the 15th.
He then closed with three tough pars for a one-over 72 to hold off fast-finishing American Steve Stricker by a stroke, with Hensby (69) a further five shots back.
Stricker started the final round eight strokes behind but seven birdies, including two on the final holes, against a lone bogey saw him sign for 65.
"It's tough to lead from the front," Harrington said.
"It's even tougher when it's Steve Stricker behind you. He tends to have one on me. I'm happy enough to get it done in the end."
Hensby opened with a four-under 67 to sit with Jay Haas on top of the leaderboard after the first round but he dropped back with rounds of 73 and 71.
In the final round he picked up two shots on the front nine and then another on 10, but a double bogey on the par-four 14th followed up with a bogey on 15 did some damage.
The Tamworth native rallied late with two birdies to close out his championship in style.
Hensby, whose lone PGA Tour victory was the 2004 John Deere Classic, announced his retirement plans during the tournament despite his rousing start.
He was top five on debut at both the US Masters (T5) and US Open (T3) and the most recent of 16 top-10 finishes on the PGA Tour came in March at the Puerto Rico Open.
But he said he was ready for life away from the tour.
"I just want to inform everyone that this will be my last year competing no matter how the rest of my year goes while playing," Hensby posted on Facebook.
"For many reasons it's time for me to pursue other endeavours which will hopefully be associated with golf.
"It's been a great journey and I for sure have no regrets as I know I've always did everything to be the best I can be.
"Golf has always been my life to an obsession and as much as I like competing there's way too many obstacles I just can't and don't want to deal with anymore."
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