We examined the role of people’s self-evaluation in predicting their attitudes toward supporters of COVID-19-related conspiracy theories by replicating and extending the findings of a study by Cichocka et al. (2016, Study 3) in two preregistered studies (total N = 1179). Study 1, a direct replication, confirmed that narcissism and self-esteem—two different sources of people’s self-evaluation—differentially predicted their beliefs in a series of well-known conspiracy theories (not related to COVID-19), and served as mutual suppressor variables. Specifically, narcissism was positively related and self-esteem was negatively related to conspiracy beliefs, especially when the respective other predictor was controlled for. Study 2 extended Cichocka’s and our Study 1’s findings by testing the differential role of self-esteem and narcissism in predicting a COVID-19-specific criterion. Specifically, we focused on people’s rejection of supporters of COVID-19 conspiracy theories, a criterion we deem particularly important in curtailing the spread of these theories. Results were generally in line with previous findings, but effects were substantially weaker. As suggested by exploratory analyses, this might be due to the fact that the overall rejection of supporters measure comprises not only items capturing rejection of supporters but also items capturing low beliefs in conspiracy theories. These two distinct components differentially related to self-esteem and narcissism: the differential role of self-esteem and narcissism could only be replicated for the “low belief” subcomponent (thus replicating findings from the original study and from Study 1) but not for the “rejection of supporters” subcomponent. The present work thus contributes to recent research suggesting that low belief in conspiracy theories and the rejection of their supporters might be qualitatively different responses with unique antecedents.