Background: Diabetes mellitus (DM) is a group of metabolic disorders of fat, carbohydraternand protein metabolism that results from defects in insulin secretion, action, or both. About 50%rnchronic care patients in the developed countries are non-adherent and it is estimated to be higherrnin developing countries. Non-adherence is one of the major causes of suboptimal glycemic control,rnwhichrninrnturnrnisrnrncompounded by acute & chronic complications of DM. rnObjectives: To assess anti-diabetic medication adherence and determinant factors among adultrntype 2 DM patients on follow up at All African Leprosy Rehabilitation and Training Centerrn(ALERT) Hospital, Addis Ababa, Ethiopia from February - December 2020. rnMethods: Cross sectional study was conducted among adult type 2 DM diabetic patients on followrnrnup at ALERT Hospital from February2020 - December 2020. Ethical clearance was obtainedrnfromrnFamilyrnrnmedicine ethical committee of College of Health Sciences of Addis AbabarnUniversity. 385 participants who were eligible & voluntary were selected. A structured standardrnquestionnaire and data extraction sheet was prepared and utilized to collect data. Adherencernwas assessed using the four-item WHO Modi fi ed Morisky Adherence predict or Scale -4rn(MMAPS-4). Data was analyzed using the SPSS v-25.0.0. Multiple regression models were usedrnto assess factors associated with adherence. rnResults: Three hundred eight five adult T2 DM patients participated in the study. 318 (82.6%) ofrnthe participants were adherent to ADM based on MMAPS-4. Forgetfulness was the major reasonrnfor non-adherence. Glycemic control was inadequate in greater than eighty percent of participants.rnrnrnLifestyles modifications, like joint dietary plan with physician, have significant associationrnwith glycemicrncontrol.rnrnConclusion: Anti-diabetic medication adherence was relatively high compared with other similarrnstudiesrninrnEthiopia.rnHowever,rnoverallrnrnglycemic control was found to be inadequate despite arnhigh medication adherence which may be due to failure to implement non -pharmacological approaches.rnrnMulti-stake holderâ€Ÿs collaboration to ensure adherence more & improvement of non-rnpharmacological approaches may help in improving glycemic control.