Objectives: The aim of this study was to investigate the prevalence and its determinants of Antipsychotic Use in patients with psychiatric disorders. Materials and Methods: This study was on patients with psychiatric disorder that have discharged from the hospital. We have assessed all patients with psychiatric interview and evaluation of their psychiatric documentations. Results: 90.7% of all of patients had taken antipsychotic medications and antipsychotic polypharmacy was in 27.2% of these patients. The most prevalent component of antipsychotic polypharmacy was consisting of Chlorpromazine, Halopreidol and Chlorpromazine, Risperidone and then Chlorpromazine, Olanzapine respectively. There were significant relations between pattern of antipsychotic use and gender, occupation status, type of psychiatric ward, duration of hospitalization and cost of treatment but no relationship with age, educational status and duration of illness. Discussion: This study suggests that prevalence of antipsychotic polypharmacy is high in in-patient psychiatric patients.