Breast cancer is an important public health issue and should be immediately overcomed. Along with lifestyle change and changes in environment conditions, at this time breast cancer has been occured at young age. In the development of technology, there are various ways to detect the existency of abnormalities in the breast in early stage, a more convenient way and efficient to detect breast abnormalities is Breast Self Examination (BSE). The aims of this study was to find out whether counseling BSE able to improve the knowledge, attitudes and behavior of young girl in the effort early detection of breast cancer on the schoolgirl at SMAN Mengwi Badung. The design of this study were used Quasi-Experimental Design with Nonequivalent Control Group Design. The population in this study were schoolgirl grade XI of SMAN 1 and SMAN 2 Mengwi. Number of sample were 140 people. 70 respondents from SMAN 1 Mengwi as the control group with only leaflet and 70 respondents from SMAN 2 Mengwi as the experimental group by giving leaflet and counceling. Data have been analyzed by using paired T-test to compare the results of pre-test, post-test, and to compare both the treatment and the control group. The results of the study shows that there were improvement in knowledge, attitudes and behavior of young girl before and after giving information and leaflets in the treatment group and the control group on BSE. In the treatment group have higher level of knowledge, attitudes and behaviors than the control group with p value 0.007 for the knowledge, p = 0.003 for attitudes, and p = 0.015 for the behavior. Based on the findings above, young girls are suggested to improve their understanding on the normal and abnormal breast condition. Primary Health care (PHC) should deliver continous counceling program to improve knowledge, attitude and practice of BSE.