After going 3-0 in six starts in May and compiling a 1.67 ERA, Haren has earned American League Pitcher of the Month honors for May.
Haren is unbeaten in games in which the A's score at least two runs and he's worked at least seven innings in eight starts this season.
"You get him a few runs and you're definitely feeling pretty good," catcher Jason Kendall said. "I know it sounds cheesy, but Dan's 'The Man' right now."
The 26-year-old right-hander gave up 11 walks while fanning 37 batters in the month. He fanned a season-high nine batters against the Devil Rays on May 4 and put together a string of three wins to finish off the month and improve his record to 6-0 on the season.
His 1.64 ERA is the lowest in the American League. Haren has never received the AL Pitcher of the Month honor before.
"He wanted to take on that role, and he's exceeded everything we could have wanted out of him," A's manager Bob Geren said. "He could be a true No. 1 on just about any staff in Major League Baseball."
Fausto Carmona of Cleveland finished second in the voting. Haren's teammate Chad Gaudin, Minnesota's Boof Bonser, Detroit's Justin Verlander, the Angels' John Lackey and Kelvim Escobar, Cleveland's Paul Byrd, Toronto's A.J. Burnett and Seattle's J.J. Putz all received votes.
Haren and National League winner Jake Peavy will receive a 52-inch Sharp TV and a specially designed trophy to commemorate the awards.
Leslie Parker is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.