Since the end of 2019 to the present day, the COVID-19 pandemic has been affecting the functioning of countries, institutions and individuals. So far, despite the increasing number of studies, little is known about the effects of the pandemic on the psychosocial well-being of a person. Research results obtained to date suggest that the fear of COVID-19 may be reduced by humor. However, to be able to harness this observation to provide more effective psychological assistance to those struggling with serious concerns about the aftermaths of the pandemic, one has to understand the mechanisms of the relationship between humor and fear of COVID-19. Both clinical experience and research findings show that the postulated relationship may be mediated by generalized anxiety. In the present study, we investigated the relationship between humor, conceptualized as a dimension of wisdom, and fear of COVID-19, and the role of generalized anxiety as a potential mediator of this relationship in adults. A longitudinal three-wave field study was carried out in a sample of 214 adults from Poland. A mediation analysis with bias-corrected bootstrapping method confirmed that the relation between humor and fear of COVID-19 was mediated by generalized anxiety.