This study examined changes in dietary life and dietary life satisfaction in one-person households during the COVID-19 pandemic. Using a sample of 916 one-person households from the Food Consumption Behavior Survey, we applied ANOVA and a system of equations model for our analysis which produced four main results. Firstly, during the COVID-19 pandemic, eating homemade and delivered meals increased, whereas eating restaurant, group, and HMR meals decreased. Eating breakfast and regular eating habits also increased during the pandemic. Secondly, approximately 30% of the sample reported increased expenditure on fresh food and HMR meals. The proportion of positive changes in dietary life was also greater than negative changes, and dietary life satisfaction was about three times higher than it had been before the pandemic. Thirdly, having breakfast and regular eating fully mediated the relationship between spending on fresh food and dietary life satisfaction, as well as the relationship between HMR purchases and dietary life satisfaction. Changes in expenditure on fresh food and HMR meals positively affected dietary life satisfaction through eating breakfast and regular eating. Fourthly, increased consumption of delivered food had a positive direct effect on dietary life satisfaction. Among sociodemographic variables, gender, education, occupation, and age were also significantly related to changes in dietary life satisfaction.