ABSTRACT BACKGROUND: Self-care is one of the most important principles of life and the successful treatment of patients diagnosed with cancer. Also, the first step and the most effective factor for self-care is health literacy. Thus, the aim of this study is to evaluate the relationship between level of health literacy and self-care ability in patients diagnosed with breast cancer.METHOD: Using an analytical-descriptive approach, the present study was conducted using a random access method among 120 patients diagnosed with breast cancer referring to Imam Reza Hospital of Tabriz University of Medical Sciences, during 2019. The data was gathered using two standard self-care questionnaires in patients diagnosed with breast cancer (SCHFIV6.2) and Health Literacy for Iranian Adults (HELIA). Data analysis was conducted using SPSS v22, through Pearson correlation tests and linear regression analysis. RESULTS: The results indicate a positive and significant relationship among dimensions of health literacy including access, reading, appraisal, decision, and understanding, and dimensions of self-care including self-care maintenance, self-care management, and self-care confidence. Other findings show that reading, access and decisions have a direct and significant effect on self-care ability (P-value ≤0.01).CONCLUSION: With regard to the direct and significant relationship of health literacy and self-care dimensions in patients diagnosed with breast cancer, enhancing their health literacy can result in improved self-care among them. In addition, due to the increasingly high prevalence of this disease among women, improving their health literacy can be effective in the treatment of this disease or in enhancing their quality of life. KEYWORDS: Health Literacy, Self-care, Breast Cancer, Breast Neoplasms, Self-care Maintenance, Self-care Management, Self-care Confidence