PURPOSE: The purpose of this study was to determine the influences of uncertainty and social support on the quality of life among elderly cancer patients. METHODS: A descriptive correlational study was conducted with 128 patients aged over 65 who were diagnosed with cancer from either the cancer center or the university hospital. Data were collected from October 8(th), to November 6(th), 2013 and analyzed using descriptive statistics, t-test, ANOVA, Pearson's correlation coefficients and stepwise multiple regression with the SPSS/WIN 18.0 program. RESULTS: Uncertainty and quality of life showed significant negative correlation (r=−.48, p<.001). The predictors of quality of life were ambiguity as subunit of uncertainty, severeness of pain and primary caregiver. These explained 41% of the variance (F=4.47, p=.037) and the most influential factor was ambiguity. CONCLUSION: This study demonstrated that the quality of life was influenced by ambiguity and personal characteristics. The result suggests that intervention programs to reduce the level of uncertainty and pain of patients could improve the quality of life among elderly cancer patients.