Objectives <p>Obesity and its associated type 2 diabetes mellitus (T2DM) represent a growing public health challenge worldwide. This study aimed to evaluate the cost-effectiveness of sleeve gastrectomy (SG) compared with pharmacological therapy (PT) in patients with obesity and T2DM from the perspective of the reimbursement institution in Türkiye.</p> Methods <p>A Markov cohort model was developed to evaluate the cost-effectiveness of SG compared with PT in patients with obesity and T2DM. The model simulated a cohort of 1,000 individuals entering the model at age 40 years over a 60-year lifetime horizon from the perspectives of the Social Security Institution (SGK) and the Public Health Service Price Schedule (PHSP). Cost data were obtained from hospital records of 44 patients receiving PT and 55 patients undergoing SG, while effectiveness inputs were derived from published literature. Costs were calculated for the 2023 price year, and both costs and health outcomes were discounted at an annual rate of 3%. One-way and probabilistic sensitivity analyses were performed to assess parameter uncertainty.</p> Results <p>According to the Markov model results, lifetime total costs were estimated at US$3,412.9 for PT and US$4,043.8 for SG. Lifetime health outcomes, measured in quality-adjusted life years (QALYs), were 11.33 for PT and 12.68 for SG. Compared with PT, SG provided an additional 1.35 QALYs at an incremental cost of US$630.9, corresponding to an incremental cost-effectiveness ratio (ICER) of US$467 per QALY gained.</p> Conclusions <p>The results indicate that SG is a cost-effective treatment option for patients with obesity and T2DM in Türkiye, providing greater health benefits at an acceptable incremental cost compared with PT. The relatively lower healthcare costs in Türkiye may further enhance the long-term cost-effectiveness of SG.</p>