Objectives: In this study, we investigated the changes in smoking behavior during the COVID-19 outbreak in Korea in 2020. We also examined the influence of general characteristics and mental health problems due to COVID-19 on changes in smoking behavior. Methods: We collected data from August to October 2020 from adults aged 19 years and older from the Korea Community Health Survey (N=229,269). Results: Among current smokers (N=39,534), 11.0% reported an increase in smoking, and 12.8% reported a decrease in smoking. Overall, 33.3% reported perceived stress and 3.7% reported depression. Participants reported COVID-related anxiety about infecting family (83.0%), economic damage (76.3%), blame or harm from others (66.5%), infection (60.6%), and death (31.3%). Lower education level, living alone, and poor subjective health status were associated with increased smoking. Being a woman and being of older age were associated with decreased smoking. Stress, depression, andanxietyabouteconomicdamageduetoCOVID-19weremorelikelytoresultin increased smoking. Anxiety related to death due to COVID-19 was more likely to result in decreased smoking. Conclusion: Thesefindingsprovide insight intothechanges in smoking behavior caused byCOVID-19.