Two assumptions guide the current research. First, people’s desire to see themselves as moral disposes them to make attributions that enhance or protect their moral self-image: When approached with a prosocial request, people are inclined to attribute their own noncompliance to external factors, while attributing their own compliance to internal factors. Second, these attributions can backfire when put to a material test. Studies 1 and 2 demonstrate that people who attribute their refusal of a prosocial request to an external factor (e.g., having an appointment), but then have that excuse removed, are more likely to engage in prosocial behavior than those who were never given an excuse to begin with. Study 3 shows that people view it as more morally reprehensible to no longer honor the acceptance of a prosocial request if an accompanying external incentive is removed than to refuse a request unaccompanied by an external incentive. Study 4 extends this finding and suggests that people who attribute the decision to behave prosocially to an internal factor despite the presence of an external incentive are more likely to continue to behave prosocially once the external incentive is removed than are those for whom no external incentive was ever offered. This research contributes to an understanding of the dynamics underlying the perpetuation of moral self-regard and suggests interventions to increase prosocial behavior.