By Dylan Lewis
Finau beat Australian Cameron Smith on the first playoff hole after they shared the lead on 20 under par through 72 holes.
Rounds of 67, 64 and 68 left the two-time PGA tour winner close to the lead going into the final day which was delayed until Monday due to storms in the New York area.
Green staff had to contend with nine inches of rainfall over Sunday and Monday morning which left the course in an unplayable state.
Once play got back under way, Finau who was paired with Shane Lowry and Justin Thomas shot a 65 to give him a share of the lead.
Finau made an eagle and three birdies in the last seven holes to force the playoff with Smith.
With this victory, the American moves to the top of the FedEx Cup rankings, just ahead of world number one Jon Rahm.
“I feel like it’s been a long time coming but I also feel like you have to earn everything out here,” said Finau. “I’m playing some great golf. We’ve got two big tournaments in front of me, so I’m going to enjoy this one.”
Only the top 70 players in the FedEx rankings move onto the next event at the BMW Championship.
English hopefuls Matt Fitzpatrick and Tyrell Hatton started the week inside the top 70 but both missed the cut for weekend play, this saw them drop out of the top 70 and ultimately ends their playoffs.
Ian Poulter also missed out on the top 70 after a poor weekend saw him move down the leader board and out of the playoff race.
The second event of the playoffs is the BMW Championship at a new venue for the PGA tour at Caves Valley Golf Club, this will take place between 26 and 29 August.