This study examined the relationship between general population characteristics and diet-related factors pertaining to eating alone for older adults (65 years and older) in Korea. This study used the Korea National Health and Nutrition Examination Survey (KNHANES), 2016–2020, and the target population was 7037 Koreans aged 65 years or older who participated in the nutritional survey and health interview. Eating alone variables were classified as follows. Eating together all day means “eating together”, eating only one meal a day means “1/day”, eating two meals a day alone means “2/day”, and “3/day” means eating three meals a day alone. The main results are as follows. The rate of moderate or severe food insecurity was 3.41% in the “eating together” group to 7.86% in the “3/day” group, which was 4.45% higher in the “3/day” group. Fruit + vegetable intake among food intake lowered by about 35 g from 301.2 g in the “eating together” group to 266.2 g in the “3 day” group. In addition, as a result of analyzing the prevalence of depression using the PHQ-9 score, the “3/day” group had a 1.775 to 2.464 times higher risk of depression than the “eating together” group. Finally, EQ-5D variables and quality of life scores were significantly lowered from the “eating together” group to the “3/day” group. Overall, higher frequency of eating alone was associated with food safety, essential food intake, and quality of life. Based on these results, it is thought that a dietary life support program such as the eating together program is necessary to improve the quality of life of the older people who eat alone.