The purpose of this study was to examine the factors affecting quality of life among elderly people with type 2 diabetes mellitus (DM) in a community. The design of this study was an exploratory survey. The subjects were 268 adults aged over 65 years with DM in a community. The data were collected from July to October, 2011 and analyzed by descriptive statistics, Pearson's correlation coefficient, and stepwise multiple regression by using SPSS/WIN 20.0 program. The quality of life was positively associated with self care behavior (r=.226, p<.001), self-efficacy (r=.323, p<.001), and socialsupport (r=.345, p<.001). However, quality of life had moderately negative correlation with depression(r=-.445, p<.001). Among the variables, depression, social support, and self-efficacy were explanatory factors accounting for 23.9% of quality of life. These findings suggest that depression and self-efficacy are important factors affecting quality of life in the elderly with DM and it can be improved by strengthening social support.