Purpose: The purpose of this study was to identify the predictive factors on quality of life (QOL) in the urban residents by age. Methods: A cross-sectional descriptive design was used. A total of 592 urban residents, ages of 20 to 59, completed a self-reported questionnaire including WHO QOL Scale-Brief (WHOQOL-BREF), Health Promoting Life Style Profile II (HPLP), Personal Competence of Health Care Scale (PCHC), and self-efficacy scale. Data were analyzed with descriptive statistics, t-tests, ANOVA, Pearson's correlation coefficients, and multiple regressions by SPSS 18.0. Results: The mean scores were 53.71 in QOL, and subscales were 14.41 in physical health, 13.31 in psychological, 13.87 in social relationship, and 12.12 in environment. There were significant differences by age groups, gender, education, family income, job, and present illness in QOL. QOL were significantly associated with HPLP, PCHC, and self-efficacy. The results of multiple regression indicated that HPLP, PCHC, marital state, and self-efficacy in the 20s, HPLP, self-efficacy, age, marital state, religion, and PCHC in the 30s, HPLP, PCHC, self-efficacy, and family income in the 40s, and HPLP, PCHC, self-efficacy, and gender in the 50s were statistically significant in predicting QOL. Conclusion: It is important to develop distinct programs by age for improving of quality of life for adults.