Returning from Tommy John surgery that caused him to miss the 2014 season, Harvey was 13-8 with a 2.71 ERA in 29 starts, helping New York reach the World Series for the first time since 2000.
Fielder hit .305 with 23 homers and 98 RBIs for Texas, which won the AL West for the first time since 2011. He played in 42 games in 2014, when his season ended in mid-May because of a herniated neck disk that needed surgery.
Major League Baseball announced the winners Thursday. The awards, which began in 2005, are voted on by the 30 team beat writers from MLB.com.
Harvey and Fielder earn Comeback Player of the Year honors
ESPN SweetSpot blogger David Schoenfield breaks down MLB's Comeback Player of the Year Awards.