Norms have a pervasive influence on behavior, yet previous research has not addressed that people often face conflicting norms from multiple ingroups. The current research addresses this gap in the context of proenvironmental behavior and demonstrates two effects predicted by the novel theoretical position we offer: People can be de-motivated by norm-conflict, or conversely, norm-conflict can encourage people to take action. Studies 1 and 2 demonstrated that norm-conflict is associated with increased perceived effectiveness for those with positive attitudes to the issue and reduced perceived effectiveness for those with moderate attitudes, and effectiveness perceptions mediated an indirect effect on behavioral intentions. Study 3 found that perceived effectiveness also moderates the effects of norm-conflict such that norm-conflict only influences intentions when perceived effectiveness is high. Norm-conflict is both positively and negatively related to behavioral decision making, suggesting additional considerations in the design of social norms-based interventions.