Background: Type 2 diabetes mellitus is a major public health problem which affects the large number of people worldwide. Diabetes mellitus patients are at high risk of experiencing drug therapy problems due to different factors. Involvement of pharmacists in the management of diabetes mellitus has been shown to reduce the incidence of drug therapy problems. Objectives: To assess the prevalence of drug therapy problems, pharmacists' intervention and determinants of drug therapy problems in the management of type 2 diabetes mellitus patients. Methods: Facility based prospective cross sectional study was conducted among ambulatory type 2 diabetes mellitus patients at Madda Walabu University Goba Referral Hospital from April 1, 2017 to June 30, 2017. Data was analyzed using SPSS version 22. Descriptive statistics was performed to determine the proportion of drug therapy problems and pharmacist acceptance rate. Logistic regressions analysis was performed to identify determinants of drug therapy problems. A p-value of less than 0.05 was considered as statistically significant. Result: A total of 216 type 2 diabetes mellitus participants were included, of these 52.8% were males. The mean age of study participants was 57.07 ± 13.126 years. Among the study participants, 88% have at least one drug therapy problems. Needs additional drug therapy was the most frequent (50.2%) followed by non-compliance (21.7%). Metformin with glibenclimide and insulin were the most frequently prescribed anti diabetic drugs accounts for 40.3% and 27.8%, respectively. The recommendation done by pharmacists were 94%, the most common intervention done was to add new drug (50.2%). The acceptance rate for the interventions done was 72.6%. Conclusion: The prevalence of drug therapy problems among type 2 diabetes patients was high. Statin and metformin use not optimized. The involvement of clinical pharmacists in problems intervention should be promoted to decrease drug related risk and increase medication adherence of the diabetic patients.