BackgroundThe effectiveness of sacituzumab govitecan for metastatic triple-negative breast cancer (TNBC) has been reported in recent research, however, the value of the effectiveness and cost of sacituzumab govitecan is still unclear.MethodsA microsimulation model was developed using data from the ASCENT trial to assess the cost-effectiveness of sacituzumab govitecan for patients with relapsed or refractory metastatic TNBC over a lifetime. Model inputs, including clinical data, patient characteristics, and direct medical costs, were based on the ASCENT trial, public databases, and published literature. The primary outcomes of the model were the incremental cost-effectiveness ratio (ICER) and quality-adjusted life-years (QALYs). Univariate and probabilistic sensitivity analysis (PSA) and multiple scenario analyses were performed to address the uncertainty of the model.ResultsOur results revealed that sacituzumab govitecan versus chemotherapy costs $293,037 and yielded an additional 0.2340 of QALYs in the whole population with metastatic TNBC, leading to an ICER of $1,252,295 gained. And in the population with metastatic TNBC without brain metastasis, the sacituzumab govitecan versus chemotherapy costs $309,949 and obtained an extra 0.2633 of QALYs, which resulted in an ICER of $1,177,171/QALYs. Univariate analyses indicated that the model outcomes were most sensitive to the drug cost of sacituzumab govitecan, the utility of progression-free disease, and the utility of progressed disease.ConclusionFrom the US payer perspective, sacituzumab govitecan is unlikely to be a cost-effective option for patients with relapsed or refractory metastatic TNBC compared with chemotherapy. Based on the value standpoint, a price decrease of sacituzumab govitecan is expected to increase the cost-effectiveness of sacituzumab govitecan in patients with metastatic TNBC.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12913-023-09728-6.