Objectives: The aim of this study is to examine health-related behaviors, and mental health of one-person household adults and health-related quality of life levels, and investigate factors influencing their health-related quality of life. Methods: A Secondary data from the 8th Korean National Health and Nutrition Examination Survey (2019, 2021) were used for data analysis. Data from 839 one-person household adults aged over 20 were analyzed. Hierarchical regression analysis was conducted to explore risk factors on quality of life. Results: Among single-person household adults, the study found that the smoking rate was 33.4%, with an alcohol consumption rate of 66.9%. Additionally, approximately 50.9% engaged in regular physical activity, 32.2% reported experiencing much stress, and 7.5% had experienced suicidal ideation. The overall quality of life was 0.81 out of 1 point. The factors influencing the quality of life were age, income, occupation, stress, and suicidal ideation. Conclusions: It appears that we need to identify whom have no job, low income, with high levels of stress and suicidal thoughts, from their early adulthood in single-person householdsand and to have attention and support for the health-related quality of life.