The right-hander didn't allow a run in August, converting all 11 of his save opportunities. He pitched 11 innings over 12 games, allowing six hits and six walks while striking out four. He's slumped a bit since the start of September, leading the Cardinals to give him a brief breather to fight off fatigue.
"It is a cool thing," Franklin said of the award.
Manager Tony La Russa noted that Franklin earned his saves in August.
"He had a bunch of tough saves," La Russa said. "Heart of the lineup, one-run [leads]."
It's been a fine stretch away from the field lately for Franklin. He recently agreed to a new two-year deal with the Cardinals, extending his stay with the club through 2011.
Franklin won the award over a list of candidates that also included the Astros' Jose Valverde, the Nationals' Mike MacDougal, the A's Andrew Bailey and the Yankees' Mariano Rivera. It's the first time he's won the honor in his career.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.