OBJECTIVES::  The aim of the study was to evaluate the incremental cost-utility ratio of obinutuzumab+chlorambucil (GClb) versus chlorambucil monotherapy (Clb) in patients with chronic lymphocytic leukemia (CLL) with no previous treatment and classified as ineligible to full dose of fludarabine under the Brazilian Public Healthcare System (SUS). METHODS::  A Markov model was developed to follow the patients with CLL through the disease course, for this reason, the model was conducted in a lifetime time horizon. The outcome evaluated was quality-adjusted life years (QALY). The treatment cost included drug acquisition cost and cost related to disease and adverse events management. Drug prices were obtained from Brazilian official price list. Cost of disease management and adverse events were calculated by a micro-costing based on specialist opinions. The efficacy data was obtained from the CLL11 and CLL5 studies, using an extrapolation of the curves through loglogistic parametric distribution. The utility data was defined from an English study, which the health states and their respective utilities were based on an EQ-5D survey. A sensitivity analysis was conducted to validate the results. RESULTS:: Total treatment cost of GClb and Clb were BRL 93’018 and BRL 2’050, respectively. Incremental QALY of GClb (4.075) and Clb (2.776) was 1.299, which resulted in an incremental cost-utility ratio of BRL 68’955/QALY. The probabilistic sensitivity analysis confirmed the base case results, since the majority of the simulations on the PSA (1’000 simulations) were located on the quadrant with higher cost and positive clinical benefit. CONCLUSIONS:: The analysis suggests that GClb can be a cost-effective option in the CLL treatment when comparted to Clb, under the SUS perspective. The use of cost–effectiveness ratios in decision-making remains an area without consensus in Brazil as there is no threshold established.