A critically important aspect of supportive care in cancer is the prompt recognition and effective treatment of psychiatric complications. Psychiatric disorders such as depression, anxiety and delirium occur in a significant percentage of cancer patients, particularly as disease advances and as cancer treatments become more aggressive. This paper reviews factors that can be utilized to identify patients who are at increased risk for developing psychiatric complications, such as those with advanced disease, certain cancer treatments, uncontrolled physical symptoms, functional limitations, lack of social support, and past history of psychiatric disorder. Methods of diagnostic assessment and strategies for managing depression, anxiety, delirium and suicidal ideation are also reviewed.