Background: Selecting appropriate patients for AC (adjuvant chemotherapy) remains an important issue in BC treatment. Although AC improves clinical outcomes toxicity and economic burden is substantial. The Oncotype DX test identifies high-risk patients likely to benefit from AC who otherwise might not be identified through standard parameters (SP), and low-risk patients unlikely to benefit from AC, avoiding toxicities and inherent risks. This study estimated the incremental cost-effectiveness ratio and budget impact (BI) of Oncotype DX testing from the perspective of the Brazilian Public Health System. Methods: A Markov transitional state model was developed with 3 states: recurrence free, distant recurrence, and death. The model compared the scenario in which patients are screened by SP with a proposed scenario with Oncotype DX testing. Changes in therapeutic recommendations and cost of treatment were obtained from a prospective clinical survey at Pérola Byington Hospital. Additional data was obtained from literature. As a societal perspective analysis, medical costs (test, AC, and adverse events), costs of productivity loss, transportation and employment leave were considered. Population was estimated from BC incidence, proportion of early stage cases, and HR expression. An incremental proportion of 10% per year of patients using Oncotype DX testing was assumed. BI analysis had a 5-year horizon and cost-effectiveness a lifetime horizon (5% annual discount). Results: Oncotype DX results as identifier of a subgroup at higher risk of relapse and greater benefit with AC was dominant over SP. Oncotype DX testing resulted in clinical benefits in terms of life-years gained (0.62) and quality-adjusted life years (0.54), related to lower incidence of distant recurrence and use of AC, both of which greatly impacted quality of life. Testing resulted in economic benefits, with lower average cost per patient (−BRL 3,855). Incorporation of Oncotype DX testing resulted in potential savings reaching BRL 107 million in the 5th year stemming from the decrease in AC and consequent decrease in indirect costs. Conclusions: Patients with HR+, HER2− early stage BC may present different risks of relapse and likelihoods of benefiting from AC. With high clinical impact for patients and high economic impact for the health system, a tool that safely and accurately identifies the subgroup of patients who really needs AC is essential. Oncotype DX test incorporation in the Brazilian Public Health System should be considered.