This study was conducted to determine the effects of the health belief and optimistic bias on COVID-19 preventive behaviors. Data were collected from 311 adults using a questionnaire. The collected data were analyzed through descriptive statistics and structural equation modeling, and multigroup analysis was performed to analyze the moderating effect. The results showed that all HBM variables, except for perceived susceptibility, had statistically significant effects on COVID-19 preventive behaviors. Perceived susceptibility, perceived severity, perceived benefits, and cues to action had statistically significant effects on the optimistic bias group, and perceived benefits, perceived barriers, and cues to action affected the group without optimistic bias. A statistically significant moderating effect was found only for perceived severity. The results of this study are expected to contribute to the establishment of crisis response policies by contributing to the establishment effective and elaborate strategies that promote individual preventive behaviors to cope with COVID-19 pandemic.