Lack of economic evaluation of unit cost in delivery of hospital services in developing countries public hospitals has led to poor resource allocation.(1) This is mainly caused by unawareness of importance of unit costs, and lack of costing experts, lack of expertise in the use of information related to economic evaluation in operating public hospitals.(2) Objective was to evaluate the unit costs of Diabetes Mellitus treatment and drivers in Muhimbili National Hospital (MNH), Tanzania. A cross-sectional descriptive hospital-based (direct cost-provider perspective) study was carried out from July to Sept 2020 in Emergency Department of MNH. The study horizon and analytical horizon were both one year (January to December 2019). Costing of materials, diagnosis and invested time were estimated from patient’s electronic files. Treatment information and analysis were done using Microsoft excel for quantitative data. Bottom up approach was used to arrive at the total and unit cost of the health condition. Estimated unit cost for treating diabetes mellitus was found to be TZS 272,831. Cost drivers includes high cost of some diabetic medications. Unit cost for providing treatment to diabetic patients at emergency department at Muhimbili national referral hospital is high. Purchasing relative cheaper anti diabetic medications. Annual unit cost studies should precede budgeting and pricing for services offered by the department. Prioritizing preventive services especially annual health checks could lower curative services costs significantly. Patients’ perspective study will shed light on what is the cost bone by diabetic patients as they seek treatment at the department.