The present research investigated whether risk perception of COVID-19 relates to subjective well-being and the mediating role of authenticity in this association. We conducted a 12-day daily diary study with 133 undergraduates (Mage = 19.9 years, SD = 1.27 years; 64 females). Participants self-reported risk perception of COVID-19, authenticity, and subjective well-being every day. Results revealed that (1) risk perception of COVID-19 was negatively related to subjective well-being at the interindividual level; (2) authenticity mediated the relationship between risk perception of COVID-19 and subjective well-being at the interindividual level but not at the intraindividual level. In general, findings suggested that risk perception of COVID-19 is negatively related to subjective well-being only at the interindividual level, and authenticity plays a mediating role in this relationship. The finding suggested that keeping authenticity is a good strategy for avoiding the disruption caused by COVID-19. Longitudinal studies on samples with a broader age range, larger sample size, and extended sociodemographic background, as well as experimental studies, should be conducted to explore the causal relationship among interested variables that the current research has not detected.