FARMINGDALE, New York, Aug 23, 2012 (AFP) - Harrington has a one-stroke lead over Nick Watney and Brian Harman, who both fired six-under 65s on the Bethpage course.
Harrington is hoping a strong showing at the event will convince European Ryder Cup captain Jose Maria Olazabal to make him one of his two captain's picks.
Sergio Garcia, of Spain, shot a 66 and shares fourth place with Pat Perez, England's Gary Christian and Jimmy Walker. Garcia won last week at the Wyndham Championship.
American Tiger Woods is part of a group tied for 14th after carding a three-under 68. Defending champion Dustin Johnson is one stroke ahead of FedEx Cup points leader Woods in eighth.
While The Barclays is the first of four PGA Tour playoff events, a more immediate concern for Harrington is the Ryder Cup. He cannot make the European team on points so he needs to show Olazabal that he is worthy to compete in his seventh straight Ryder Cup.
"The only answer I can give at this stage is I'm pleading the Fifth Amendment on that one," Harrington said.
"I honestly don't know what to say. I don't want to go in there and try too desperately to beg for a pick, or I don't want to go in there and give excuses for anything. I'll just leave it be what it is. I'm just going to play golf."
Woods' playing partner Rory McIlroy shot a 69. Woods scrambled to save some early pars and McIlroy got off to a good start, finishing with five birdies and three bogeys.
Woods and McIlroy will be playing together during the opening two rounds because the event groups players based on their FedEx Cup standings -- Woods is in first place while McIlroy is currently third.
Joining Johnson in eighth place were Rickie Fowler, Justin Rose, George McNeill, K.J. Choi, and Jonas Blixt.
Phil Mickelson, Luke Donald, Ernie Els and Vijay Singh are among those tied for 14th with Woods.
The event also marks the start of the FedEx Cup playoffs. The top 100 in the standings advance to the second round at the Deutsche Bank Championship and then the top 70 move on to the BMW Championship.
The top 30 reach the FedEx Cup final at the Tour Championship, with the winner pocketing $10 million.
First-round scores on Thursday in the PGA Tour's The Barclays tournament (USA unless noted, par-71):
64 - Padraig Harrington (IRL)
65 - Brian Harman, Nick Watney
66 - Gary Christian (ENG), Sergio Garcia (ESP), Pat Perez, Jimmy Walker
67 - Jonas Blixt (SWE), K.J. Choi (KOR), Rickie Fowler, Dustin Johnson, George McNeill, Justin Rose (ENG)
68 - Luke Donald (ENG), Ernie Els (RSA), Zach Johnson, Chris Kirk, Troy Matteson, William McGirt, Phil Mickelson, Greg Owen (ENG), Ian Poulter (ENG), John Senden (AUS), Vijay Singh (FIJ), Tiger Woods