In the present research, we focus on COVID-19 vaccine hesitancy and empirically examine how different forms of social identity (defensive vs. secure national identity and identification with all humanity) and conspiracy beliefs are associated with COVID-19 vaccine hesitancy. In two cross-sectional nationwide surveys (Study 1, n = 432, and Study 2, n = 807), we found that willingness to vaccinate against COVID-19 was negatively linked to national narcissism, but positively related to secure national identification, that is, national identification without the narcissistic component. In both studies, we also found that the relationship between narcissistic (vs. secure) national identity and unwillingness to vaccinate against COVID-19 was mediated by COVID-19 vaccine conspiracy beliefs. These effects were present even when we accounted for basic demographics (Studies 1 and 2) and identification with all humanity (Study 2), which had been found to be a significant predictor of health behaviors during COVID-19. In line with previous research, identification with all humanity was positively associated with the willingness to vaccinate against COVID-19. We discuss the implications for understanding the role of the way in which people identify with their national and supranational groups in antiscience attitudes and (mal)adaptive behaviors during COVID-19 pandemic.