The first goal of this study is to develop a conceptual model of the causal relationship between psychological antecedents (internal attribution, anger, dangerousness, fear) of stigmatization, stigmatization (public stigma, anticipated stigma), and the behavioral consequences (compliance with COVID-19 prevention guidelines, COVID-19 testing intention) of stigmatization associated with COVID-19. The second goal of the study is to investigate the age differences in the conceptual model between younger and older adults unconfirmed with COVID-19 in Korea. After building the model based on previous studies, an online survey was conducted with Koreans in their 20s (n = 300, females: 50%) and 60s (n = 300, females: 50%) who had not been confirmed with COVID-19. The results revealed that for participants in their 20s and 60s, their internal attribution of COVID-19 infection to individuals confirmed with COVID-19 enhanced their anger at the individuals. Afterward, their anger increased their anticipated stigma of being confirmed with COVID-19 through enhancing the public stigma of the individuals confirmed with COVID-19. Unexpectedly, the fear of individuals confirmed with COVID-19 elicited by the dangerousness of the individuals had no effect on the public stigma of the individuals among participants in their 20s and 60s. The fear directly enhanced their compliance with the COVID-19 prevention guidelines. Next, for participants in their 20s, their anticipated stigma increased their compliance with COVID-19 prevention guidelines, but not their COVID-19 testing intention. However, the anticipated stigma did not affect both the compliance with the COVID-19 prevention guidelines and COVID-19 testing intention among participants in their 60s. The implications and limitations of these findings are discussed.