Considering that the number of middle-aged single-person households is increasing, this study investigates dietary behaviors, nutrient intake, and mental health according to household type. Data were procured from the 2015-2019 Korea National Health and Nutrition Examination Survey (KNHANES). Totally, 5,466 participants aged 50-64 years were classified into 2 groups: a household with one member was defined as a single-person household, and households with two or more members were described as multi-person households. Single-person households comprised 10.63% of the total, with a higher average age, and lower income and economic levels than multi-person households. Compared to multiperson households, single-person households had a higher frequency of skipping breakfast, eating alone, and dining out, the moderately and severely food insecure group was more than 5 times, and nutrient intake and dietary quality were poorer. In the fully adjusted model, the odds ratios (ORs) of depressive symptoms were 2.35 times (95% CI: 1.39-3.96), and suicide ideation was 1.95 times (95% CI: 1.35-2.82) in single-person compared to multi-person households. Our results lead us to conclude that poor dietary intake in middle-aged single-person households affects the mental health, and the above factors should be considered when framing the dietary policy.