Background: Breast self-examination is the most important screening method for early detection and diagnosis of Breast cancer. Females assess their breasts regularly to detect any abnormalities to seek instant medical attention. Objectives: The main objective of the study was to assess the knowledge on breast self-examination among female adolescents of Nepal. Method: A cross-sectional study was conducted using self-structured questionnaires among female adolescents of Model Multiple College, Dhanusha. The sample size was 120 participants. Probability proportionate stratified sampling technique was used to collect the data from October 28th to November 12th, 2013. Data were processed through Statistical Package for Social Sciences version 16 and analyzed using descriptive statistics. Results: Out of 120 participants 67.5% participants had knowledge about breast cancer and 40% had knowledge of breast self-examination (BSE). Most of them (94.2%) had a poor knowledge of BSE followed by 5.8% of participants with a moderate level of knowledge of BSE. The mean knowledge score was 18.7 ± 3.5. The majority (66.7%) of participants were from science faculties. More than half (51.7%) of participants stated source of information on BSE was health personnel. Only 25% of the respondent had a family history of breast cancer. Conclusion: The study revealed that most (94.2%) of the participants had poor knowledge of breast self-examination. There is further need for awareness and health education on breast self-examination.