OBJECTIVES: The TAC adjuvant chemotherapy regimen compared to FAC improves the disease free survival (DFS) and overall survival (OS) rates significantly in women with operable node positive breast cancer, but the cost-effectiveness of this better efficacy was not evaluated. METHODS: We developed a model describing the clinical history of women with node positive breast cancer that projected improvements in lifetime quality adjusted life years (QALY), long-term costs, and cost-effectiveness of the adjuvant treatment TAC compared to FAC. The base case was a 50 years old woman with unilateral node positive breast cancer submitted to mastectomy and without metastasis. Transition probabilities came from the BCIRG 001 study and other major studies; the quality of life for each health state was based on the medical literature. The local management and costs of each health state was based on a Delphi panel according to the private healthcare perspective. Outcomes were discounted at 3% annually. Sensitivity analyses and a second order Monte Carlo simulation were performed. RESULTS: The lifetime horizon analysis showed: DFS of 32.5% and 29% and OS of 38% and 33%, for TAC and FAC, respectively; TAC increased life expectancy (LY) in 1.20 years and in quality adjusted life years (QALY) there was a 1.08 year gain, in comparison to FAC; the incremental cost per QALY was R$9476.92; the FAC group expense in the metastasis state, in fifteen years, was bigger than the whole cost for the treatment of recurrence states, for a whole life, with TAC; the Monte Carlo simulation showed that TAC is cost-effective 98% of the times and is cost-saving 18% of the times. CONCLUSION: Improvements in DFS and OS with adjuvant TAC regimen in women with operable node positive breast cancer improves patient outcomes in terms of LY and QALY with an acceptable cost-effectiveness ratio in Brazil.