BETHESDA, June 30, 2014 (AFP) - The 33-year-old Englishman and Stefani, seeking his first PGA triumph, finished 72 holes deadlocked on four-under par 280 after both fired one-under 70s on Sunday.
Rose hit into the trees and the water at the last regulation hole but sank a 15-foot bogey putt to stay tied for the lead, then watched the American match his watery fate at the same 18th hole to lose the playoff.
After claiming the $1.1 million top prize, Rose will take a week off before playing the Scottish Open as his final warm-up for the 143rd British Open at Royal Liverpool starting July 17.
"It's a huge boost confidence-wise for sure," Rose said. "I haven't really been playing with a lead all year. To do it and get it done and make key putts, that's huge for my psyche going into a major championship."
Rose won his first major title last year at Merion, struggled trying to defend the US Open crown two weeks ago at Pinehurst, but on Sunday won his sixth US crown.
"It has not been lost on me that I have not won for over a year so it was nice to get on the right side of that very quickly," Rose said.
Rose also won the 2010 National when it was played at Aronimink Golf Club near Philadelphia.
"It's the first double-winner I am of any tournament and to be double-winner of this one, it means a lot," Rose said.
A Congressional Country Club layout that hosted three US Opens, most recently when Rory McIlroy won in soggy conditions in 2011, played hard and fast and as formidable as many majors in the final round.
- 'Congressional tested all of us' -
"If I had not won the US Open, I might be looking to claim this as a US Open," Rose said.
"I think Congressional wanted its reputation back. It tested all of us."
To begin the playoff, Stefani pulled his tee shot left into trees. He took relief from a grandstand obstruction, but then sent his approach into the water left of the green where Rose ventured earlier.
"It's one of the most intimidating looking shots in golf," Rose said of the second at 18.
With a second chance from the fairway, Rose put his approach on the green and two-putted for par and the victory.
"It was nice to get a second lifeline at it," Rose said.
"It's great to win on a golf course like this because you can't sort of luck into it. All aspects of my game were tested this week and it's really nice to win in that fashion."
Rose lost his only prior playoff to Dane Anders Hansen in a 2007 European Tour event at Wentworth.
"A playoff can be won and lost within one swing and fortunately I was on the right side of that," Rose said.
In his round, Rose made a bogey at the third, but answered with birdies at the par-5 sixth and ninth holes.
A day after a double-bogey disaster at 11, Rose dropped his approach to five feet and made a rare birdie at the hole to move one back of leader Patrick Reed.
When Reed began the back nine with back-to-back double bogeys, Rose took the lead and sank a tense nine-foot par putt at 17. Stefani answered with a 14-foot birdie putt at 16 to match Rose but made bogey at 17 while Rose made his clutch bogey putt at 18.
Stefani and fellow Americans Ben Martin, Brendan Steele and Charley Hoffman booked British Open spots based on their top-five finishes.
Leading scores on Sunday after the final round of the $6.5 million US PGA National at par-71 Congressional Country Club (x-won at first playoff hole, USA unless noted):
280 - x-Justin Rose (ENG) 74-65-71-70, Shawn Stefani 74-68-68-70
281 - Charley Hoffman 72-72-68-69, Ben Martin 72-68-70-71
282 - Andres Romero (ARG) 70-72-72-68, Brendan Steele 74-66-71-71, Brendon Todd 72-70-69-71
283 - Billy Hurley 69-73-70-71, Brendon de Jonge (RSA) 71-68-71-73, Marc Leishman (AUS) 70-66-73-74
284 - Robert Garrigus 73-70-70-71, Jordan Speith 74-70-69-71, Billy Horschel 70-68-74-72, Ricky Barnes 67-69-75-73, Hudson Swafford 69-68-73-74, Richard Lee 74-68-68-74, Freddie Jacobson (SWE) 67-71-71-75, Patrick Reed 68-68-71-77
285 - Stewart Cink 74-69-71-71, John Huh 72-72-70-71
286 - Brandt Snedeker 70-70-75-71, Tyron van Aswegan (RSA) 68-74-73-71, Steven Bowditch (AUS) 73-71-70-72
287 - Russell Knox (SCO) 73-67-78-69, Angel Cabrera (ARG) 74-71-69-73, Tim Wilkinson (NZL) 70-71-72-74, Michael Putnam 69-72-72-74, Brady Watt (AUS) 71-71-71-74, Hunter Mahan, 71-73-69-74