Background: Breast cancer disease is the most common cancer among Iranian women. Management of this disease requires expensive services and care, imposing a significant financial burden on the households. This study calculated out-of-pocket (OOP), catastrophic health expenditure (CHE), and impoverishing health spending attributed to breast cancer in Iran.Methods: In this cross-sectional household study, clinical and financial information on breast cancer and also household information (expenditures and income) were obtained through face-to-face interviews and completing a questionnaire by 138 women with this disease in 2019. To defining the CHE, we applied three non-food expenditure thresholds of 40%, 20%, and 10%. Disease costs included periodical visits, diagnostic services, hospitalization care, treatment and rehabilitation services, home, and informal care. Households were disaggregated into socioeconomic status quintiles based on their monthly consumption expenditures, where SES classifications were standardized by Adult Equivalent values of consumption expenditures. For statistical comparisons of the incidence of CHE and impoverishing spending, we applied the independent t-test and one-way ANOVA respectively for two and more than two separate subgroups. Besides identifying the factors affecting these indicators, we performed the two different multivariate logistic regression models.Results: This study finds that each patient had an average OOP payment of $US 97.87 for the requested services, leading to impoverished of 5.07% and exposed to CHE of 13.77% of their households. These indicators have been mainly concentrated among the poor, as they have spent a large part of their meager income on buying the needed services, and for this purpose, most of them have been forced to sell their assets, borrow, or take a bank loan.Conclusions: Vulnerable people should be supported by expanding insurance coverage, governmental supporting programs, and increasing access to quality and effective public sector services.