Introduction: -Diabetes mellitus (DM) is the most common medical complication of pregnancy and is defined as abnormal metabolism of carbohydrates which results in elevated blood glucose level. Classified as Pre-gestational Diabetes Mellitus (Type I or Type II) or Gestational Diabetes Mellitus (GDM): a carbohydrate intolerance resulting in hyperglycemia of variable severity with onset or first recognition during pregnancy.Diabetes increases perinatal and neonatal morbidities including; macrosomia, congenital anomalies, birth injury, hypoglycemia, intrauterine fetal death, still birth, shoulder dystocia, respiratory distress syndrome, polycythemia, and hyperbilirubinemia. However, little is known about its prevalence, birth outcomes, and associated factors in the study setting. Objective:-The aim of the study was to assess the perinatal outcome and associated factors of diabetic mellitus among mothers who gave birth at Tertiary Hospitals, Bahir dar, northwest Ethiopia, 2023. Methods: - Institution based cross sectional study was conducted on 117mothers with any form of diabetes mellituswho got labor and delivery services at TGSH and FHCSH from March1 to June30, 2023.Study participants was selected with consecutive sampling technique.All mothers with DM excluding those who fulfil exclusion criteria were included. Questionnaire and checklist was used to get information from the study participants and their medical documentwith interview and chart review method. Data was entered, cleaned, coded and analyzed using statistical package for social sciences (SPSS) version 25. Binary and multivariate logistic regression analysis was computed. P-value less than 0.05 at 95 % CI was used to declare statistical significance association. Result: Overall adverse perinatal outcome was 71(60.7%). From this 11(9.4%) were stillbirths, 27(23.1%) macrosomia/LGA and 51(43.6%) were admitted to NICU. Having <4 ANC contacts [AOR =6.83; 95% CI 1.28,36.34] and FBS > 100 mg/dl [AOR = 4.23; 95% CI 1.28, 13.94] were associated with adverse perinatal outcomes. Conclusion: - Mothers with diabetes mellitus are at higher risk for adverse perinatal outcomes.Maternal blood glucose control and number of ANC follow-up are strongly associated with adverse perinatal outcome.So early diagnosis, optimal ANC follow up and good glycemic control is important to alleviate the burden of adverse perinatal outcomes. Keywords:- Diabetes m