OBJECTIVES: Bariatric surgery has been incorporated in the Brazilian Public Health System (BPHS) for patients with BMI > 40 (or BMI > 35 if diabetic) 15 years ago. However, access to the procedure is currently difficult, with waiting times reaching 7 years after clinical indication in some regions. Our objective was to compare costs and effectiveness of different time delays in surgery with immediate surgery. METHODS:  We created a Markov microsimulation model to compare four different treatment situations (hereafter referred as treatment strategies): immediate surgery and 2, 4 and 7-year delay in surgery. The surgery affected four parameters in the model: BMI, diabetes, systolic blood pressure (SBP) and the lipid profile. BMI subsequently affected survival rates and diabetes incidence; and diabetes, SBP and lipid level affected cardiovascular events. Characteristics of the population (age, sex, blood pressure, lipid levels, BMI, diabetes status) followed Brazilian statistics for patients undergoing bariatric surgery. Markov states and tracker variables reflected changes in BMI, diabetes status (including remission and relapse) and cardiovascular events. Model parameters were derived from meta-analyses and long-term studies, such as the Swedish Obese Subjects trial. Effectiveness was calculated in QALYs, where utility was influenced by current BMI. Time horizon was 20 years, the perspective was of the BPHS and discount rate was 5%. RESULTS: Immediate surgery was the least costly and most effective strategy. Costs increased and effectiveness diminished with longer delay; 7-year waiting time was the costliest and least effective strategy. Immediate surgery maintained dominance in 90.7%, 96.1% and 94.2% of simulations in probabilistic sensitivity analyses against 2, 4 and 7-year delays, respectively. CONCLUSIONS: Delay in bariatric surgery provision results in long-term greater costs and are less effective than immediate surgery in the BPHS. Strategies to accelerate access to surgery should be pursued.