BACKGROUND/OBJECTIVES The purpose of this study was to examine the effects of knowledge about coronavirus disease 2019 (COVID-19), attitude, subjective norm, and perceived behavioral control on behavioral intentions to practice COVID-19 preventive behaviors using the theory of planned behavior (TPB). SUBJECTS/METHODS A total of 519 restaurant customers' responses was collected in this study through an online self-administered questionnaire. Descriptive statistical analysis was performed on socio-demographic factors. One-way analysis of variance and t-test were conducted to determine differences in the constructs from the TPB according to age and sex. The hypotheses were tested using structural equation modeling (SEM). RESULTS SEM revealed the positive effect of knowledge about COVID-19 on attitude, subjective norm, and perceived behavioral control to prevent the spread of COVID-19 in restaurants. Attitude, subjective norm, behavior intention, and knowledge positively affected COVID-19 preventive behavior intentions in restaurants. CONCLUSIONS The results of this study confirmed that the TPB is helpful in elucidating the determinants of consumers' intention to practice COVID-19 preventive behavior in restaurants. These findings can help policy makers and professionals provide material for further public health interventions and inform them about awareness-raising, guidelines, and health education programs.