It has often been argued that compassion is fundamental to morality. Yet people often suppress compassion for self-interested reasons. We provide evidence that suppressing compassion is not cost free, as it creates dissonance between a person's moral identity and his or her moral principles. We instructed separate groups of participants to regulate their compassion, regulate their feelings of distress, or freely experience emotions toward compassion-inducing images. Participants then reported how central morality was to their identities and how much they believed that moral rules should always be followed. Participants who regulated compassion-but not those who regulated distress or experienced emotions-showed a dissonance-based trade-off. If they reported higher levels of moral identity, they had a greater belief that moral rules could be broken. If they maintained their belief that moral rules should always be followed, they sacrificed their moral identity. Regulating compassion thus has a cost of its own: It forces trade-offs within a person's moral self-concept.