Background Although the adverse effects of cancer diagnoses and treatments on mental health are known, about less than 10% of patients are estimated to be referred to seek help. The primary purpose of this study was to obtain the baseline information on patients with cancer seeking help for mental health who presented for the first time to the psycho-oncology outpatient clinic, and to identify risk factors that may provide clues healthcare practitioners in recognizing those needing psychological help in oncology practice. Methods We reviewed the charts of 566 patients with cancer who were referred to the psycho-oncology outpatient clinic over a two-year period. The study includes the socio-demographic data, illness characteristics, psychiatric characteristics, psychiatric diagnoses, and treatment recommendations for these patients. Results The incidence of diagnoses of psychiatric disorders was 97.5%. The distributions of psychiatric diagnoses were as follows: any kind of adjustment disorders, mood disorders, anxiety disorders, organic brain syndrome, personality disorders, delusional disorder, and insomnia. Recurrence of cancer, other chronic medical illnesses, a history of psychiatric disorders, poor social support, and low income comprised the common significant risk factors for adjustment disorders, mood disorders, and anxiety disorders. These risk factors were also seen to be significant in the regression analysis in terms of sex. Conclusion This study identifies the distribution of psychiatric disorders, the risk factors for specific psychiatric disorders, and draws attention to the fact that there are serious delays in patients seeking psychiatric help and in the referrals of oncologists for psychological assessment. Identifying risk factors and raising oncologists' awareness toward risk factors could help more patients gain access to mental health care much earlier.