Descriptive and injunctive social norms communicated among groups are known to influence behavior, yet little is known about how they evolve over time and how financial incentives influence norms. This article tests hypotheses about the ways in which monetary incentives can disrupt normative impact while facilitating cooperative behavior. The results of a public goods experiment indicate that the presence of a financial incentive for behavior can reduce the impact of perceived descriptive norms on behavior, and this reduction continues once the incentive is removed. The findings show that group identification enhances the effects of perceived descriptive norms on contribution behavior. The study results form the basis for theory building on the role of financial incentives in normative systems (FINS).