<![CDATA[Breast cancer was the most common cancer affecting women worldwide. The high mortality rate from breast cancer in Indonesia was largely associated with delayed detection, resulting in many cases being diagnosed at an advanced stage. Breast Self-Examination (BSE) was considered a simple, inexpensive, and effective method for the early detection of breast cancer, which could improve treatment outcomes. This study aimed to analyze the relationship between female adolescents' knowledge and attitudes toward breast cancer and their Breast Self-Examination (BSE) practices at SMAN 9 East Jakarta in 2025. A quantitative study with a cross-sectional design was conducted. The study population consisted of 264 female students, and 79 respondents were selected using a purposive sampling technique. Data were analyzed using univariate analysis and the Chi-square test with a significance level of 95% (α = 0.05). The results showed that 69.6% of the respondents had good knowledge, 73.4% demonstrated positive attitudes, and 64.6% had performed Breast Self-Examination. Bivariate analysis revealed significant relationships between knowledge and BSE practices (p = 0.011) and between attitudes and BSE practices (p = 0.001). It was concluded that better knowledge and positive attitudes were associated with improved BSE practices among female adolescents. Therefore, schools should collaborate with healthcare professionals to provide continuous health education and promotion programs to increase awareness and encourage regular Breast Self-Examination for early breast cancer detection.]]>
