Guilt is widely recognized as an important self-regulatory emotion, yet alternative theoretical accounts view guilt primarily as either a punishment cue or a prosocial motivator. Integrating these views, we propose that guilt functions dynamically to first provide a negative reinforcement cue associated with reduced approach motivation, which transforms into approach-motivated behavior when an opportunity for reparation presents itself. We tested this hypothesis in the context of racial prejudice. White subjects viewed a multiracial series of faces while cortical activity was recorded using electroencephalography. Following bogus feedback indicating anti-Black responses, subjects reported elevated guilt, which was associated with changes in frontal cortical asymmetry indicating reduced approach motivation. When subjects were presented with an opportunity to engage in prejudice-reducing behavior, guilt predicted greater interest in prejudice reduction, which in turn was associated with an approach-related shift in frontal asymmetry. The results support a dynamic model in which guilt is associated with adaptive changes in motivation and behavior.