Fake displays of emotions are common in social and organizational settings. It is therefore important to understand their consequences. To reconcile mixed previous findings, we develop a model in which the consequences of expressing fake emotions depend on the observers' level of dialectical thinking, a cognitive style characterized by acceptance of inconsistencies. We propose that observers lower, but not higher, on dialectical thinking may infer that interaction partners who fake emotions are untrustworthy and, in turn, react negatively. We found support for our model in 2 studies. In a field fundraising experiment (Study 1), fundraisers who displayed fake (vs. genuine) happiness received smaller monetary donations and elicited lower intentions to volunteer from donors lower, but not higher, on dialectical thinking. In a laboratory negotiation experiment (Study 2), negotiators who displayed fake anger (vs. genuine anger or no emotion) were trusted less and received higher demands from counterparts lower, but not higher, on dialectical thinking. Trust mediated the moderating effect of dialecticism on the relation between fake anger (vs. genuine anger and no emotion) and demands. We discuss the theoretical and practical implications of the findings.