The 22-year-old American is the second youngest to capture both awards in the same year, following Tiger Woods who was 21 when he accomplished the feat in 1997.
During his sensational five-win 2014-15 campaign, Spieth won the U.S. Masters and U.S. Open to secure his first majors, missed a playoff by one shot at the British Open and then finished runner-up at the U.S. PGA Championship.
Spieth, who also enjoyed triumphs at the Valspar Championship and John Deere Classic, capped his season with an $11.48 million (£7.6 million) payday by winning the Tour Championship and FedExCup playoffs on Sunday to go back to world number one.
Jason Day, who finished his season with four wins in seven events, including the Australian's first major at the PGA Championship, was runner-up in the player of the year award that is based on a points system.
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Bubba Watson was third followed by British Open winner Zach Johnson and Rickie Fowler.
Spieth posted an adjusted scoring average of 68.911 through 91 complete rounds to edge out Day (69.161), who had 75 rounds, for the Vardon Trophy.
Texan Spieth is also the front-runner to earn PGA Tour player of the year honours when they are announced on Oct. 2.
The other nominees are Day, Fowler and Northern Ireland's Rory McIlroy.
(Reporting by Frank Pingue,; editing by Tony Jimenez)
