Leonard stayed patient with his putting on a windy Sunday in Virginia and watched it pay big dividends with a birdie-par-eagle finish for a four-under 68 and a one-shot victory over fellow major winners Ernie Els (72) and Thomas Bjorn (68).
Leonard won for the second time this year and moved into top 10 in the Charles Schwab Cup season points standings.
The top 54 in the standings advance to the next postseason event next week in Arkansas - among them Australians Steve Allan (ranked 10), Cameron Percy (11), Richard Green (20), Mark Hensby (22), Michael Wright (27), Greg Chalmers (28), Rod Pampling (49) and Stuart Appleby (51).
Their countryman David Bransdon was a hard luck story, dropping to 55th in the standings after a closing round of 76 which left him tied 55th for the tournament.
Wright did best of the Aussies on Sunday, finishing with a 69 to be tied eighth, five shots behind Leonard.
Hensby (70), was a shot further back while Allan (73) and Percy (72) were tied for 14th.
Els was in control on the back nine of the James River course at the Country Club of Virginia and appeared to steady himself with birdies on reachable par-4 15th and the par-5 16th.
But he bogeyed the 17th as Leonard made his move. After a birdie on the 16th, Leonard hit a hybrid 4-iron to about 20 feet and holed the downhill eagle putt to post at 12-under 204.
Els failed to make a 10-foot birdie putt on the closing hole that would have forced a playoff.
Bernhard Langer, the 68-year-old German who has won every year on the PGA Tour Champions since turning 50, was within two shots of the lead until a long three-putt bogey ended his hopes. He shot 72 and finished three back in his bid for a first Champions win this year.
The top 36 after next week reach the season-ending Charles Schwab Cup Championship.
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