The relationship between norms, self-sanctioning, and people’s decisions about contributing to public goods is complex and often misunderstood in the public goods literature. We develop a model in which individuals hold an injunctive norm indicating how much they believe one should contribute to the public good. From the model we derive the following testable hypotheses: an increase in one’s perception of the norm level of contribution to the public good (1) induces negative self-sanctioning and (2) will lead one to contribute more to the public good, and (3) that contributing to the public good induces positive self-sanctioning. To test these hypotheses, we elicit stated preferences for contributions to an organization which offsets carbon emissions and a proxy for self-sanctioning, change in respondent “self-image.”