Feliz, 22, received 20 out of 28 first-place votes, 7 second-place votes, and one third-place vote for a total 122 points on a 5-3-1 scoring system. He joined Detroit Tigers outfielder Austin Jackson -- a Denton Ryan High School product -- as the only players named on all 28 ballots.
"It's incredible," Feliz said. "I have to thank my teammates for the job we've done together. It was a great season. I feel happy getting this recgoniton and I'm very proud of it."
First baseman Mike Hargrove had been the Rangers' only rookie recipient, winning the award in 1974.
Feliz, the first pitcher and fourth player from the Dominican Republic to win the award, began the 2010 season as a late-inning setup man for closer Frank Francisco. But after a rough first week of the season for Francisco, the Rangers flipped roles, moving Feliz into the closer's role. He flourished, finishing with a rookie-record 40 saves, bettering the record of 37 set by Seattle's Kazuhiro Sasaki in 2000.
He had the seventh-lowest WHIP (0.880) among pitchers with at least 50 innings and was third among AL relievers with a .176 opponent batting average. Feliz, who finished with a 4.73 ERA in 70 appearances, also led the AL by closing out 59 games.
Feliz lit up radar guns throughout the majors, regularly hitting triple-digits with his fastball. As the season progressed, he became more effective as his secondary pitches improved. He had a 1.42 ERA in the second half of the season and a .148 opponent batting average, tops among AL pitchers after the All-Star break. He didn't allow a run in his final 16 regular-season games after Aug. 22.
Rangers manager Ron Washington said Feliz undoubtedly played a key role in the team's success.
"He was a big reason we made it to the World Series," he said. "We put him in a tough job and he did it. He didn't know he was going to be closing and all of a sudden early in the season he is and he gets 40 saves for us. He deserves this award."
Feliz entered spring training ready to compete for a spot in the starting rotation, but he didn't have the pitching repertoire needed at that time to beat out the competition. Now that he's established himself as a tremendous late-inning reliever, he comes into 2011 penciled in as the closer. But the Rangers have not closed the door on the idea of Feliz starting at some point in the future.
Feliz was acquired by the Rangers from the Atlanta Braves as part of the Mark Teixeira trade in 2007. One of the other players in that deal, shortstop Elvis Andrus, was second in the rookie of the year balloting in 2009.
Feliz was on the AL All-Star team, but did not pitch in the game. He retired the San Francisco Giants in order in the top of the ninth inning of Game 3 to become the second-youngest pitcher to save a World Series game, dropping Rangers club president Nolan Ryan to third on the list. The Los Angeles Dodgers' Bob Welch was 21 when he saved a World Series game in 1978.
The runner-up Jackson hit .293 for the Tigers this season, finishing with four home runs, 34 doubles, 10 triples, 41 RBIs and 27 stolen bases.