Purpose: The purpose of the study was to identify the levels of anxiety, depression and uncertainty of patients who participated in the clinical trials for anticancer drug, and to identify correlations among these variables. Methods: Cross-sectional survey used the Symptom Check List-90-Revision and the Mishel Uncertainty in Illness Scale from 106 subjects in 2011. The data were analyzed using descriptive statistics, t-test, ANOVA, Pearson correlation coefficients. Results: The mean score of anxiety was 2.06, that of depression 2.35, and that of uncertainty 2.61. Anxiety and depression (r=.70), anxiety and uncertainty (r=.44), depression and uncertainty (r=.60) were significantly correlated each other. The levels of anxiety, depression and uncertainty were different in various characteristics of the subjects, such as education, recurrence, and economic burden. Conclusion: The results of the study indicate that when implementing psychosocial interventions for cancer patients who participate in clinical trial, factors such as education, economic burden, and recurrence should be integrated into the intervention. Further studies applying theoretical model would be helpful to identify directional relationships among the variables that are important in psychosocial well-being of cancer patients undergoing clinical trial.