Often people are faced with conflict between prosocial motivations for helping and selfish impulses that favor not helping. Three studies tested the hypothesis that self-regulation is useful for managing such motivational conflicts. In each study, depleted self-regulatory energy reduced willingness to help others. Participants who broke a habit, relative to participants who followed a habit, later reported reduced willingness to help in hypothetical scenarios (e.g., donating food or money; Studies 1 and 3). Controlling attention while watching a video, relative to watching it normally, reduced volunteering efforts to help a victim of a recent tragedy- but drinking a glucose drink undid this effect (Study 2). Depleted energy reduced helping toward strangers but it did not reduce helping toward family members (Study 3). Helping requires self-regulatory energy to manage conflict between selfish and prosocial motivations-a metabolically expensive process-and thus depleted energy reduces helping and increased energy (glucose) increases helping.