In his first season with the Oakland Athletics, Bradley posted a .276 batting average with 14 home runs and 52 runs batted in, in a part-time role. He went on the 15-day DL on May 11, 2006 for a strained oblique muscle and a sprained right knee. On July 30, he hit a three-run walk-off home run to beat the Toronto Blue Jays with two outs in the bottom of the ninth inning. During game four of the 2006 American League Championship Series versus the Detroit Tigers, Bradley became the third player in MLB history to hit home runs from each side of the plate in a postseason game, joining Bernie Williams and Chipper Jones. For the series, he went nine-for-eighteen with two home runs and five RBIs.