BACKGROUND AND PURPOSE: With the rapid increase in the number of elderly people in Korea, multiple socio-economic problems have emerged. In 2015, 6.4 million people accounting for about 13% of the total population in Korea were aged 65 years and over. As the elderly population continues to grow, the elderly who live alone are also increasing. They have potential risks in medical and neuropsychological aspects. The purpose of this study was to investigate the association between cognition and socio-environmental status in the elderly who live alone. METHODS: This study was conducted on 512 people who live alone (equivalent to 1% of the total elderly people) in Daejeon Metropolitan City between April and November 2015. Structured questionnaires were used to investigate the general characteristics, socio-economic status, physical status, and mood for participants. Simple tests using Mini-Mental Status Examination-Demetia Screening, Geriatric Depression Scale and Korean-instrumental activities of daily living were also performed. RESULTS: Among the 512 participants, 109 participants (21.3%) had cognitive impairment, and 128 participants (25.0%) had depression. The number of daily meals, frequency of meeting with family, and depression were independent risk factors for cognitive impairment. Factors including the duration of living alone, cognitive impairment, poor self-perceived health status, frequency of meeting with family and duration of education were considered an independent risk factor for depression. CONCLUSIONS: This study showed that the elderly who live alone are susceptible to cognitive impairment and depression, and factors including the number of daily meals, social contact, and self-perceived health status may affect cognition and depressive mood. Thus, physicians need to pay attention to management of major factors that may cause cognition impairment and depression in the elderly who live alone; in addition, they require ongoing community interest and support.