BACKGROUND: In Ethiopia, there is inadequate information on non-adherence tornantidepressant treatment in patients with depressive disorders. Having awareness of the pattern ofrnadherence is important in future prognosis, quality of life and functionality in these patients. Thisrnstudy will be conducted to assess the prevalence of Non-Adherence to Antidepressant treatmentrnand its predictors among Psychiatry Outpatients with Depressive Disorders. rnrn rnMETHODS: A hospital-based cross-sectional quantitative study was conducted at the psychiatryrnclinic of Tikur Anbessa Specialized Hospital. A sample of 216 consecutive outpatients withrnDepressive disorders who visited the Psychiatry clinic since June 2019 and who had at least twornvisits prior to their last visit were enrolled. Data was collected using questionnaires through inpersonrnandrnphonernrncall interviews. The eight-item Morisky scale, a scale extensively used in thernEthiopian setting, was used to assess the pattern of medication adherence. Other speciallyrndeveloped tools were used to obtain sociodemographic and clinical information from electronicrnmedical records and patient interviews. Data was analyzed using the Statistical Package for thernSocial Sciences (SPSS), Version - 25. Univariate and multivariable analyses were carried out tornassess factors associated with non-adherence.rnrnRESULTS: Ninety percent of the participants who were taking antidepressant medication werernfound to have a primary diagnosis of Major Depressive Disorder. Based on the 8-item MoriskyrnMedication Adherence Scale, the prevalence of non-adherence was found to be 84.7%. Livingrndistance between 11 to 50 kms from hospital (AOR= 11, 95% CI (29,46.6)), post-secondary levelrnof education (AOR= 8.3, 95% CI (1, 64.4)), taking multiple medications (AOR= 6.1, 95% CI (1,rn34.9)) were found to have significantly increased odds of non-adherence.rnrnCONCLUSION: The prevalence of non-adherence is very high among patients with depressiverndisorders. Non-adherence was significantly associated with factors such as increased livingrndistance from the hospital, relatively higher educational level, and polypharmacy. Proper andrnpatent centered psychoeducation to patients, addressing the communication gap between patientsrnand doctors, cliniciansâ€™ adherence to prescribing guidelines, avoiding polypharmacy unlessrnindicated, and working on accessibility of treatment for common mental disorders is essential torndecrease non-adherence. Larger analytical studies to further establish causal relationships to nonadherencernandrnitsrnimpactrnon depressionrntreatmentrnoutcomesrnarernrecommended.