Objectives: The purpose of this study was to compare drinking behaviors between one-person households and those living together to identify the harmful alcohol use of one-person households. Methods: This study analyzed cross-sectional data from 228,558 Korean adults aged 19 years and older who participated in the 2015 Korean Community Health Survey. The data were analyzed using a chi-square test to determine the patterns of alcohol use by household types and age groups. Moreover, multinomial logistic regression was used to uncover factors of harmful alcohol use for one-person households. Results: One-person households composed of young and middle-aged people had higher monthly alcohol drinking, harmful alcohol use, and yearly alcohol-related harm and drunk driving experiences. Elderly people in one-person households had high harmful alcohol use in both men and women. The factors affecting the harmful alcohol use of one-person households were similar to those of sociodemographic variables (age, residential area, marital status, occupation, educational level, monthly income) in both sexes, but physical and mental health-related factors showed differences according to the number of chronic disease diagnoses, subjective health level, subjective stress, and sleeping time according to sex. Conclusion: A number of factors are associated with the harmful alcohol use of one-person households and age groups. Owing to environmental changes, studies on the harmful alcohol use of one-person households and age groups should be continued.