The 22-year-old American ended his campaign in triumphant style with victory at the season-ending Tour Championship in Atlanta last week where he also clinched overall FedExCup playoff honours and the $10 million (£6.6 million) jackpot.
Spieth made 21 of 25 cuts on the PGA Tour, including four runner-up spots, as his earnings for the season ballooned to $22 million because of the FedExCup bonus.
He set a record for official earnings on the U.S. circuit, his tally of $12,030,465 eclipsing the previous mark of $10,905,166 established by Vijay Singh in 2004.
Spieth claimed Player of the Year honours over rivals Jason Day of Australia, Northern Ireland's Rory McIlroy and fellow American Rickie Fowler in a vote of his peers.
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Of that trio, Day pushed Spieth hardest in the battle for the prized accolade as he also triumphed five times on the 2014-15 PGA Tour while claiming his first major title at the PGA Championship.
"It was a season to remember," Spieth told reporters on a conference call. "You don't recognise it, I guess, as the year goes on. When you look at it in review, you can see exactly what we have done.
"It's an honour to win Player of the Year because it is the MVP (most valuable player) of our league and it's voted upon by the players. For them to recognise the hard work that we put in and what we've been able to do with it is truly special."
Spieth, the youngest Player of the Year since a 21-year-old Tiger Woods won the award 1997, also earned the Arnold Palmer Award as the Tour's leading money winner and claimed the Byron Nelson Award for adjusted scoring average (68.938).
REMARKABLE CONSISTENCY
Known for his brilliant putting and mental strength, Spieth displayed remarkable consistency as he dominated golf for most of the year. He came close to recording the first ever calendar grand slam of the four professional majors, his worst finish a tie for fourth at the British Open.
A surprising dip in form over the past month coincided with a red-hot run by Australian Day, who won four of six events, including the PGA Championship and two of the FedExCup playoff tournaments.
That stung the highly-competitive Spieth, who made a mental adjustment as he turned things around after missing the cut in the first two FedExCup playoff events.
"As far as the majors go, it certainly very much exceeded expectations," Spieth said of his season. "I obviously am most proud of the two wins, but I am also extremely proud of taking those two wins into the last two and not giving up, continuing to play our best golf.
"Really in my mind I should have won the (British) Open championship had I played the last two holes like we had battled that week, but unfortunately I missed a putt on 17 and didn't play 18 the right way.
"And then I ran into a buzz-saw in Jason Day at the PGA (Championship). Our best stuff was there. It certainly exceeded my expectations in the major championships."
American Daniel Berger, 22, the only rookie to qualify for the season-ending Tour Championship after recording two runner-up spots along the way, was selected Rookie of the Year.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)
