Breast self-examination is the most important screening method for detection of breast changes and abnormalities. Female who performs breast self-examination are familiarized with appearance and feel of their breasts. So, knowledge on breast self-examination helps them to detect breast changes earlier to seek instant medical help. The objective of the study was to find out knowledge and attitude on breast self-examination among female students in secondary school of Kathmandu. A descriptive cross-sectional study design was used among 103 female students of Cosmic Int’l Academy, Kathmandu using non-probability purposive sampling technique. Data was collected using self-developed structured questionnaire adopting self-administered method. Data was processed through Statistical Package for Social Sciences version 25 and analyzed using descriptive as well as inferential statistics and represented in tabulated form. The findings of the study showed that adequate knowledge was found on meaning of breast self-examination (52.5%), appropriate age to start breast self-examination (55.3%), indication (61.2%) and correct direction for performing breast self-examination (60.2%). However, inadequate knowledge was found on purpose (30.1%), ideal time (29.1%) and appropriate position (15.5%) for breast self-examination. Hence, more than half (50.5%) of the female students had adequate knowledge on breast self-examination. Likewise, more than half (51.5%) of the female students had positive attitude towards breast self-examination. The study show that more than half of the female students have adequate knowledge as well as positive attitude towards breast self-examination. However, there is lack of knowledge on purpose, ideal time and appropriate position for performing breast self-examination. So, there is need of awareness and health education on breast self-examination to improve knowledge for successful breast self –examination practices.