Studies investigating the psychological aspects of cancer have gained importance in recent years. In these studies, the rates of depression and anxiety in cancer patients were examined, but the risk of suicide had not been examined. This study investigated the psychiatric diagnoses of depression, anxiety, and suicide risk in cancer patients. Eighty patients who met the inclusion criteria were administered the Beck Depression Inventory, State-Trait Anxiety Inventory, Structured Clinical Interview for DSM (SCID), and Suicide Probability Scale. The examination of the relationships across variables was assessed with Pearson's correlation analysis and stepwise multiple regression analysis. Due to SCID assessment, 45% of patients were found to have depression diagnosis, and 11.25% were found to have anxiety diagnosis. In the patients who had previous psychiatric diagnosis and treatment, total suicide probability scores demonstrated statistically significant differences. The frequency of depressive disorders and anxiety disorders in cancer patients is high. The studies investigating that suicide are rare, and in our findings, previous psychiatric diagnosis and treatment were risk factors. In the past studies, depression has been reported to be the most important factor in increasing the risk of suicide in cancer. Contrary to previous findings, according to the data obtained from this study, anxiety is the most important predictor of suicidal risk among all the determinants.