'I didn't experience that before in winning a tournament,' admitted Harrington, who pocketed $1,035,000 for the win. 'Normally you have a short putt or two putt to win. But the excitement of following that putt down, was very special.'
Brad Faxon and Brian Gay carded matching rounds of 2-over-par 73 on Sunday. They shared third place with Kenny Perry, who shot an even-par 71. The trio was knotted at 5-under-par 279.
Furyk let Harrington back into the tournament as the 2003 U.S. Open winner stumbled at No. 16. Furyk had a two-shot lead, but three-putted from almost 80 feet, to see his lead fall to one.
At the par-4 17th, Furyk's approach landed 44 feet from the hole. His birdie putt missed by close to 7 feet and Furyk's par-saver never touched the hole.
The duo was knotted coming down Westchester Country Club's par-5 closing hole. Furyk did not find the fairway with his drive, so he laid up with his second. He wedged his third to 15 feet, but Harrington reached the green with a 3-iron.
Harrington, a three-time European Ryder Cupper from Ireland, rolled in his long eagle putt to win. Furyk congratulated Harrington on the victory, then sank his birdie putt to lose by a single stroke.
'I wanted just me and Jim to be fighting out for it and being a bit more like a match,' said Harrington. 'You could analyze it all day, you've got to go with what it feels like and trust that you've got the feeling right, because if you start trying to think about it, you could hit it 15 feet by or even let it come off the tier or short.'
Furyk knew he let the opportunity at his first victory since 2003 go on 16 and 17.
'There's no consolation,' said Furyk, who has not won since wrist surgery at the beginning of last year. 'I don't know how to elaborate on that, other than finishing second really stinks.'
Furyk and Harrington began the final round tied at 9 under par, but Harrington made a mess of his early holes. He missed a 35-foot birdie putt by 10 feet at No. 2 and left with bogey. One hole later, Harrington three-putted again, this time it was for double bogey.
But Harrington tied Furyk atop the leaderboard at the par-5 ninth. Harrington got on in two with a 6-iron and converted the 10-footer for eagle. Furyk two-putted from 35 feet to make birdie on the same hole, to take a one-shot lead.
Harrington padded Furyk's advantage when he missed the fairway with a 3-wood at No. 11. The Irishman dropped another shot at the difficult 12th to find himself three back.
Harrington hit a wedge inside 5 feet to set up birdie at the 14th. He was down two, but thanks to Furyk's miscues coming in, Harrington collected his second win this season and second since playing the PGA Tour full time. He won the Honda Classic in March.
He also got a bit of redemption from a year ago. In a playoff last year, Harrington missed a 5-footer in a playoff and eventually lost to Sergio Garcia.
'This week, I decided to lighten up a bit and try and enjoy it more,' said Harrington, whose thoughts are back home with his father who is battling cancer. 'I always play better when I've got a smile on my face rather than maybe the last couple of months which have been pretty tough. The nature of things that happen, it's easy to get down on yourself.'
Dean Wilson shot an even-par 71 and finished alone in sixth at minus-4.
Vijay Singh (73), a two-time winner of this event, John Senden (73), Billy Mayfair (66) and Justin Leonard (71) shared seventh place at 3-under-par 281.
Garcia only managed a 1-under 70 and tied for 22nd place at plus-2.