Religion is a powerful influence on social attitudes and behavior. Paradoxically, religion is correlated with both aggressive and prosocial tendencies. We argue that different concepts of God as authoritarian (controlling, commanding, punishing) or benevolent (helping, forgiving, protecting) play distinct, yet crucial, roles in leading people to behave either aggressively or prosocially. We provide new evidence among Catholics and non-Catholic Christians linking concepts of an authoritarian God with aggression and of a benevolent God with volunteerism and the willingness to aid religious outgroups. We also experimentally manipulate concepts of God and show that for non-Catholic Christians, reminders of a benevolent God increased the willingness to forgive while reminders of an authoritarian God increased aggression and decreased forgiveness, the willingness to conserve water, intentions to volunteer, and the willingness to aid religious outgroups. We conclude with a discussion of how God-concepts affect both positive and negative social behaviors.