The aim of this study was to examine the extent of psychiatric patients' compliance and non-compliance with treatment and examine the factors that affect compliance. Patients were recruited who were between 16 and 60 years of age and who were hospitalized with a psychiatric disorder and treated in the outpatient clinics of the psychiatry department. A total of 689 patients were approached and 564 patients agreed to participate in the study, a response rate of 81.8%. Participants were asked to complete a questionnaire that asked about socio-demographic characteristics (e.g., age, gender, nationality, level of education, occupation, marital status, and life style habits); medication(s) prescribed and the participant's response; the degree of social supervision (rated subjectively by the patient as "poor," "good," or "very good"); data also were obtained from clinical records. Data analyses explored significant associations between compliance and non-compliance and a group of relevant variables. Of the 564 patients studied, 328 (58.2%) were compliant with treatment and 236 (41.8%) were non-compliant. There was no significant difference between compliance and non-compliance in terms of gender (p = 0.471). Patients between 21-30 years of age were significantly more compliant with drug treatment than not. Non-compliance was more common among patients diagnosed with schizophrenia (28.4%), followed by depression (14.4%), and bipolar affective disorder (12.7%) (p = 0.001). Only 25% of compliant patients and 26.3% of non-compliant patients used non-psychotropic medication. Social supervision (40%) was very poor in non-compliant patients whereas 49.4% of compliant patients had very good family support. Notable reasons for non-compliance were irregular attendance to clinic (55.5%), ignorance about side effects of medication (61%), free medicine (45.8%), and a lack of education about medication (58.1%). This study revealed that non-compliance rates among psychiatry patients were comparable to the rates reported in other studies. The findings suggest that there is a need to provide community-level mental health education and proper counseling to psychiatry patients.