Abstract: Treatment non-adherence for chronic illnesses such as diabetes is a common problem. The aim of the study was to assess the pattern of non-adherence to diabetic therapy and associated factors among type 2 diabetic patients. A cross sectional study was conducted from February 01 to April 30, 2011, at Jimma University Specialized Hospital diabetic clinic. Data on Socio-demographic characteristics, disease related and medication related factors, complexity of regimen and drug side effects were collected. Medication non-adherence was measured using a self-reported 4-item Morisky scale. Patient characteristics, number and dosing of all prescribed medications, glycemic control levels, diabetes related complications, co-morbid conditions and diabetes related admissions were reviewed from patient records. Univariate and multivariate logistic regression model was used to identify the factors related to non-adherence. Among the total of 267 type 2 diabetic patients (mean age 52.4±11.9), the prevalence of non-adherence was 24.3% (n = 267). About half of the patients 140 (52.4%) were on Metformin/Glibenclamide based combination therapy. Patients with depressive symptoms (AOR = 2.404, 95% CI = 1.323-4.366, p = 0.004) and who experienced side effects (AOR = 1.868, 95% CI = 1.012-3.446, p = 0.046) were twice more likely to be non adherent than without depressive symptoms and without manifesting side effects, respectively. Similarly, diabetic patients on complex regimen were three times non adherent (AOR = 3.413, 95% CI = 1.652-7.050, p = 0.001) than those with simple regimen. In conclusion, non-adherence in the current study was high particularly among patients with depressive symptoms, side effects and on complex regimen. Thus, continuous adherence monitoring and support services need to be implemented to such group of patients.