Introduction: Breast self-examination (BSE) is an effective and simple method for the early detection of breast cancer. However, its practice remains low, particularly among women of reproductive age (WRA). This study aims to determine the relationship between knowledge about breast cancer and interest in performing BSE among WRA in the working area of Penebel II Public Health Center during February to March 2025. Method: A cross-sectional design was used, with a sample size of 51 WRA respondents selected through purposive sampling, calculated using a correlational analytic formula. Data analysis was conducted using the Spearman Rank test. Result: The results showed that the majority of respondents had a moderate level of knowledge (56.9%) and a high interest in performing BSE (51%). The Spearman Rank statistical test revealed a significant relationship between knowledge of breast cancer and interest in performing BSE (p < 0.001), with a correlation coefficient of 0.691, indicating a strong positive relationship. Conclusion: knowledge about breast cancer affects interest in doing SADARI so that health institutions can enhance ongoing education to encourage WRA to perform BSE as an early detection effort for breast cancer.