OBJECTIVES : Patients adherence studies are essential for evaluating the quality of care delivery of a health facility and patients’ role in improving their conditions. The objective of this study is to determine the level of adherence of outpatients to psychotropic drugs and evaluate the impacting factors. METHODS : The study was a cross-sectional study done at the psychiatric hospital, Uselu, Benin city, Nigeria from April to September, 2013. Convenient sampling method was used in population size determination for data collection. The participants were adult patients ( 18 years  and above) attending the outpatients psychiatric clinic of the hospital with diagnosis of various psychiatric illnesses. A total of 250 patients participated in the study and a well-structured self-report 10-item questionnaire using the medication adherence rating scale (MARS) was used. Additional information was patients’ socio-demographic profile and clinical variables that affect patients’ adherence to medications. Adherence to medication data were analyzed with respect to gender and level of adherence and factors that impact patients’ adherence. RESULTS The level of patients’ adherence to psychotropic was 63.6% and factors found to significantly affect adherence include amount spent per clinic visit, perception of social support, intake of alcohol, medication side effects, and existing denial of illness and use of traditional medicine. CONCLUSIONS The level of adherence to psychotropic medications was fairly high and factors that were significantly related to adherent status were amount spent per clinic visit, perception of social support, intake of alcohol, medication side effects, existing denial of illness and use of traditional medicine. The study provides a baseline data for further studies on patients’ adherence to psychotropic medications.