Derk Pereboom argues that since we are not ultimately morally responsible for our thoughts and actions, it is irrational and unfair to feel and express moral anger towards agents for their wrongdoings. Furthermore, he argues, moral anger is not practically beneficial, typically causing more harm than good. Thus, he proposes that we replace moral anger with moral sadness, or disappointment in response to agents’ wrongdoings. I offer a functional account of moral anger to argue that moral anger has important intrapersonal and interpersonal functions that cannot be served by moral sadness. I show that when we feel and express moral anger in the right contexts, it a) promotes long-term wellbeing, b) benefits relationships, and c) is the best way to change agents’ future behavior. I conclude by discussing implications of my functional account for Pereboom’s claim that moral anger is rational and fair only if we are ultimately morally responsible.