How we make decisions that have direct consequences for ourselves and others forms the moral foundation of our society. Whereas economic theory contends that humans aim at maximiz- ing their own gains, recent seminal psychological work suggests that our behavior is instead hyperaltruistic: We are more willing to sacrifice gains to spare others from harm than to spare ourselves from harm. To investigate how such egoistic and hyperaltruistic tendencies influence moral decision making, we investigated trade-off decisions combining monetary rewards and painful elec- tric shocks, administered to the participants themselves or an anonymous other. Whereas we replicated the notion of hyperal- truism (i.e., the willingness to forego reward to spare others from harm), we observed strongly egoistic tendencies in participants’ unwillingness to harm themselves for others’ benefit. The moral principle guiding intersubject trade-off decision making observed in our study is best described as egoistically biased altruism, with important implications for our understanding of economic and social interactions in our society.