Background: A quantitative study to assess the effectiveness of educational intervention regarding knowledge about sexual abuse among the adolescent girls in mother Teresa matriculation and higher secondary school, Pudukkottai. The main objective of this study is to assess the level of knowledge on sexual abuse among adolescent girl sand to evaluate the effectiveness of educational intervention on sexual abuse among adolescent girls. Pre experimental one group pre-test and post-test design was used. Non probability purposive Sampling Technique was used 50 adolescent girls were agreed to participate in this study at Mother Teresa Matriculation and Higher Secondary School. Results: Out of 50samples, the level of knowledge among adolescent girls 1(2%) belongs to excellent knowledge, 6(12%) belongs to good knowledge14 (28%) belongs to average knowledge, 30(60%) belongs to poor knowledge in pre-test. Where as in the post-test, 8(16%) belongs to excellent knowledge, 30(60%) belongs to good knowledge, 8 (16%) belongs to average knowledge, 2(4%) belongs to poor knowledge. Thus, effectiveness of educational intervention on the level of knowledge was confirmed by the paired’ test value 22.8 which was found significant at p<0.05. There is significant association between the post-test knowledge level among the adolescent’s girls and their demographic variables. Conclusion: A educational intervention was very effective in increasing the knowledge among adolescent girls.