Does a diagnosis of brain dysfunction matter for ascriptions of moral responsibility? This chapter argues that, while knowledge of brain pathology can inform judgments of moral responsibility, its evidential value is currently limited for a number of practical and theoretical reasons. These include the problem of establishing causation from correlational data, drawing inferences about individuals from group data, and the reliance of the interpretation of brain findings on well-established psychological findings. Brain disorders sometimes matter for moral responsibility, however, because they change an individual’s moral psychology in a way that is beyond their control. While control over psychological changes is not an excusing factor, brain disorders can mitigate moral responsibility because they confront individuals with new psychological deficits or urges for which their previous moral education and existing external and internal moral resources have not prepared them.