Purpose: The purposes of this study were to examine the relationships between health literacy, self-efficacy, social support, and medication adherence and to determine its impact on medication adherence in the elderly. Methods: This study was a descriptive research study. Structured questionnaires were used for survey with a convenience sample of 220 elderly in a community. Data were analyzed using descriptive statistics, ANOVA, Pearson's correlation coefficient, and stepwise multiple regression with IBM SPSS 18.0. Results: The mean scores of health literacy, self-efficacy, social support, and medication adherence were $35.89{\pm}19.39$, $55.34{\pm}7.44$, $86.54{\pm}15.90$ and $4.82{\pm}1.83$, respectively. There were significant correlations between health literacy, self-efficacy, social support, and medication adherence. Social support (${\beta}=.23$, p=.001) and health literacy (${\beta}=.21$, p=.002) were significantly associated factors with medication adherence. Conclusion: This finding showed that nursing interventions to promote medication adherence in the elderly group should focus on social support program and health literacy intervention.