Two studies investigated how values affect competitive versus cooperative behavior. Each Study presented a new social-dilemma game, in which participants' interpretations of the dilemma (i.e., their subjective payoff matrix)-and consequently the dominant (i.e., rational) behavioral choice-depended on their values. The Paired Charity Game (Study 1) framed the situation in terms of cooperation. As hypothesized, contribution correlated positively with universalism and benevolence values that reflect concern for others and negatively with power, achievement, and hedonism values that promote self-interests. Furthermore, values, but not traits, predicted the participants' contribution. The Group Charity Game (Study 2) was designed to frame the situation in terms of competition. As hypothesized, contribution correlated positively with emphasizing benevolence over power values. Moreover, the impact of values was stronger when they were rendered accessible, indicating a causal influence of values on behavior. Furthermore, when their value hierarchy was rendered accessible, participants explained their choices in terms of those values that were (a) important to them and (b) relevant to the situation. The findings thus point to the mechanism through which accessible values affect behavior. Taken together, the studies promote our understanding of the value-behavior relationships, by highlighting the impact of values on perception.