Purpose: The purpose of this study was to identify degrees of fatigue and influencing factors for fatigue in cancer patients. Method: Data was collected by questionnaires from 115 cancer patients at 3 hospitals in Seoul. The research instruments utilized in this study were fatigue, physical symptoms, depression, family support, and health promoting behaviors. Data was analyzed using the pearson correlation, t-test, ANOVA, and stepwise multiple regression with SPSS/WIN 12.0. Result: The mean score of fatigue for cancer patients was 12.90(range: 6-36). Fatigue for cancer patients according to age group and weight change showed a significant difference. Fatigue for cancer patients showed a significantly positive correlation to physical symptoms and depression. There was a negative correlation between family support and health promoting behaviors. The significant factors influencing fatigue for cancer patients were physical symptoms, health promoting behaviors, depression, and age group, which explained about 45.9%. Conclusion: The results suggest that symptoms and depression management, nursing interventions and practices for providing health promoting behaviors according to age are needed to manage the fatigue in cancer patients.