Most studies on COVID-19 preventive behaviors have focused on single-level factors such as national policy, community social capital, or individuals' sociodemographic characteristics. Through a social-ecological model, this study attempts to comprehensively examine the multilevel factors associated with COVID-19 preventive practices in South Korea. Accordingly, a web survey involving 1,500 participants was conducted in December 2020. An ordinary least squares (OLS) regression was used to examine the multilevel factors (individual, interpersonal, community, and policy levels) related to COVID-19 preventive measures, which are based on wearing a mask, washing hands, covering the mouth when coughing or sneezing, and social distancing. When factors at each level were investigated, higher scores of COVID-19 fear and correct knowledge at the individual level, COVID-19 information share at the interpersonal level, and better evaluation of the national government policies in regard to COVID-19 at the policy level were positively associated with COVID-19 preventive behaviors. Community-level factors-neighborhood perception and community participation-were negatively significantly related to COVID-19 preventive behaviors. Additionally, older age, being female, and having a graduate-level education were positively related to better preventive behaviors. The findings of the current study suggest that multilevel efforts are needed to promote preventive behaviors. Specifically, more effort to alleviate COVID-19-related fear and disseminate correct knowledge among Korean citizens is needed as the individual-level characteristics explained the preventive behaviors more than the factors at upper levels.