Existing theories of social value orientations posit that prosocials maximize joint outcomes whereas proselfs maximize outcomes to themselves. Three studies employing a total of 157 undergraduates were conducted to test the alternative hypothesis that prosocials prefer equal outcomes to maximizing joint outcome. In study 1 participants completed the Triple-Dominance Measure of Social Values in which a fourth alternative that distributed the largest joint outcome unequally was added to the alternative that distributed the outcomes equally. In accordance with the hypothesis, prosocials preferred the equal-outcome alternative to the joint-outcome alternative. Study 2 confirmed and extended these results by demonstrating that prosocials preferred equal outcomes to larger joint outcomes that were unequally distributed but provided both with larger outcomes. Study 3 demonstrated that in a modified prisoner's dilemma game, a preference for equal outcomes to a larger joint outcome resulted in that prosocials cooperated when they believed or knew that the other cooperated, and defected when they believed or knew that the other defected.