The win, combined with his success in last week's PGA Championship, made Singh the first player in 1998 to achieve back-to-back US tour victories.
"I'm really happy for this one," Singh said. "I have never won two in a row. It sure feels nice."
Singh is the first man to win two tournaments in a row since last year, when South Africa's Ernie Els won at Westchester straight after his US Open victory.
A 25-foot eagle putt on the 17th hole was worth five points for Singh on the Modified Stableford scoring system used in the Sprint International, giving him a total of 47 for the event, six ahead of the joint-runners- up, Willie Wood and Phil Mickelson.
Mickelson, the 1996 and 1997 winner, finished with an eagle followed by a birdie, but Singh would not surrender the bogey his rivals needed from him, and duly produced the eagle to seal his victory.
Singh insists his dramatic rise to the top will not change his life, even though he will try to win three in a row at next week's PGA World Series of Golf in Akron, Ohio.
"I don't see why it should change anything," Singh said. "I'm just going to go out there next week and try and do the same thing."
Gary Player shot a final round of 68 to win the Long Island Classic in New York by one stroke, and become the second-oldest player ever to win a Senior tour event. "Obviously it's a big thrill for me to win at this age. I really played well," Player, who will be 63 in November, commented.