The award is presented annually to the athlete, team or coach who transcended the year in both athletic performance and character.
Bumgarner led the Giants to the World Series title in October, earning a pair of victories in his two starts against the Kansas City Royals before finishing off the seven-game triumph with a five-inning save on two days' rest in the finale.
"What we saw from Madison this year -- and in particular in the World Series -- is the stuff of legends," said Paul Fichtenbaum, Time Inc. Sports Group Editor. "It's rare to see someone so young establish himself as one of the best ever, but after three outstanding World Series performances the case can be made that he's the best postseason pitcher of all-time."
The 25-year-old left-hander has 67 regular-season wins and has been a part of three World Series championships. In 36 career World Series innings, Bumgarner is 4-0 and holds all-time records for lowest ERA (0.25), fewest hits per nine innings (3.5) and fewest walks plus hits per inning (0.528).
Bumgarner is the first Giant and seventh big league pitcher to earn Sportsman of the Year honors.
The other pitchers to win the award were Johnny Podres in 1955, Sandy Koufax in 1965, Tom Seaver in 1969, Orel Hershiser in 1988, and Curt Schilling and Randy Johnson in 2001. In all, there have been 15 baseball selections -- 14 players and the 2004 Boston Red Sox -- the most recent being Derek Jeter in 2009.