Objectives: The emergence of COVID-19 and its consequences has led to fears, worries, discomfort, depression, and anxiety for human beings worldwide. In this study, we examined the relationships among COVID-19 stress, leisure constraints, and happiness of Korean adults. Methods: We employed on-line convenience sampling to recruit participants. The sample consisted of Korean adults. A total of 600 surveys were distributed, we retained 293 responses for analysis. Results: COVID-19 stress subcomponents significantly impacted on individual happiness. Our findings align with research focusing on positive correlates between perceived COVID-19 stress and leisure constraints subcomponents. We also found that as COVID-19 stress decreased, perceived happiness increased. Conclusions: Future research is proposed to explore the mechanism of how leisure constraints influence the engagement of physical activities and strategies of leisure constraints negotiation to gain the benefits of happiness in the pandemic crisis. Managerial implications and future research are discussed from the perspectives of constraint negotiation and happiness.