Two studies examined interactions of implicit power motivation and experimentally varied victory or defeat in a contest on implicit learning of a visuomotor sequence associated with the contest outcome and changes in testosterone and self-reported affect. In men and women, power motivation predicted enhanced learning (sequence-execution accuracy) after a victory and impaired learning after a defeat. In men, power motivation predicted testosterone increases among winners and decreases among losers, and testosterone decreases mediated the negative effect of power motivation on learning in losers. In women, power motivation predicted postcontest testosterone increases, particularly among losers. In both men and women, self-reported affective states were influenced only by contest outcome and were unrelated to participants' testosterone changes or implicit learning.