In this cross-sectional, descriptive study, we compared the sociodemographic characteristics, social networks, health-promoting behavior, and the health-related quality of life of older Korean adults living in South Korea to those of older Korean adult immigrants living in the USA. A total of 354 older adults, aged 65 years or older, participated. Data were collected through self-directed questionnaires, and analyzed using a two way analysis of variance, t-tests, χ -tests, and Pearson's correlation coefficient. The association between four sociodemographic characteristics and health-related quality of life was significantly different between the two groups. For the older Korean adults living in South Korea, positive correlations existed between a measure of their social networks and both health-promoting behavior and health-related quality of life. For the older Korean immigrants, the findings revealed a positive correlation only between social networks and health-promoting behavior. The study findings support the important association social networks can have with health-related quality of life, and their possible relationship to health-promoting behaviors of older Korean adults. We suggest that health policy-makers and healthcare providers develop comprehensive programs that are designed to improve older adults' social networks.