Purpose: This study aimed to understand how changes in income due to the COVID-19 pandemic have affected the health behavior and mental health status of self-employed individuals. Methods: We compared the health behavior and mental health status of regular wage workers and self-employed individuals with no change in income, with that of self-employed individuals with reduced income due to the spread of COVID-19. Results: Smoking status, average amount of smoking per day, changes in the amount of smoking and drinking due to COVID-19, drinking frequency per year, monthly binge drinking experiences, subjective stress, and suicidal thoughts experienced by self-employed individuals with decreased income were not only higher than those of wage workers and self-employed individuals with maintained income, but their happiness index was also lower than the latter group. Conclusion: This study suggests that the change in total household income due to COVID-19 adversely affects the health behavior and mental health status of self-employed individuals. However, COVID-19-related policies focus only on economic loss compensation, and the health behavior and mental health management for self-employed individuals is insufficient. Therefore, it is necessary to establish policies for health behavior and mental health management of self-employed individuals.