Objective:To explore the causes and influencing factors of financial toxicity in young breast cancer survivors, and to provide evidence for intervention program development to improve financial toxicity in young breast cancer survivors.Methods:Using descriptive qualitative research methods, 29 young breast cancer patients from September to December 2021 in Breast Surgery Follow-up Clinic of Fudan University Shanghai Cancer Center were interviewed. The Nvivo 12.0 qualitative data analysis software was used to analyze the data.Results:Four themes were extracted as following, direct cost of cancer treatment was the primary cause of financial toxicity, indirect costs related to cancer and treatment cannot be ignored, long-term effects of cancer and treatment further exacerbated financial toxicity, and cancer-related financial toxicity was also influenced by a variety of other factors.Conclusions:Multiple causes affected the experience of financial toxicity in young breast cancer survivors. The occurrence and risks of financial toxicity in young breast cancer survivors should be assessed. Intervention and support should be provided to meet the needs of young breast cancer survivors.