Kelly tied Smith's hit to 3 feet for birdie on the par-4 16th and moved ahead with a 15-foot birdie putt on the par-3 17th. After Smith left an 8-foot birdie try short on the par-5 18th, Kelly pulled his 3½-foot birdie attempt to the left and tapped in for the winning par.
"I really wanted that last one," Kelly said. "I didn't listen to my caddie. I thought it was outside the left. Now I understand why Jerry Smith left his putt short, because he was almost borderline going uphill, which you really couldn't see that."
Kelly had a tournament-record 19-under 197 total at TPC Snoqualmie Ridge. He opened with a 65 for a share of the lead and had a 66 on Saturday to take a three-stroke advantage into the final round. The three-time PGA Tour winner from Madison, Wisconsin, was making his 13th senior start after turning 50 in November.
"It's definitely my first wire-to-wire win," Kelly said. "Does it count, wire-to-wire, even though I lost the lead at one point today?"
Yes, it does count.
"Really, it's because my wife started traveling again," Kelly said. "This is the first really full week that we're together after just dropping my son off at Boulder, Colorado, for college. Really that, I wanted to do a little something to hopefully ease her mind about what we just went through in dropping off one of the coolest kids I've ever met."
Smith closed with a 64.
"You've got to commend him for birdieing 16 and 17," Smith said about Kelly. "I know he missed a short one on 18. Would have felt better if he had made it, but I hit a poor putt there, so I felt bad on that. ½ Just kind of leaves a bad taste in your mouth. You think Jerry's going to make it. You'd like to make him make it, but he ended up missing it."
Bernhard Langer (65) and Billy Mayfair (66) tied for third at 16 under. Langer won the event in 2010 and 2016. He has a tour-high four victories this year, winning three of the tour's five majors. The German star turned 60 on Sunday.
"I was trying to shoot my age today, but I couldn't do it," Langer said. "Have to wait. Haven't done it yet. I just thought that would be a cool way to celebrate my 60th birthday."
Colin Montgomerie (66) was fifth at 15 under.
Local favorite Fred Couples tied for 20th at 8 under after a 70.