Introduction and Background of the study: Anorexia Nervosa is defined as an eating disorder causing people to obsess about weight and what they eat. Aim: The study to assess the effectiveness of structured teaching programme on knowledge regarding eating disorders among adolescent girls. Material and Methods: A quasi-experimental one group pre-test post-test research design was adopted on 60 students by using convenient sampling technique. A self-administered structured knowledge questionnaire was used to assess the knowledge followed by structured teaching programme. The analysis of data was computed by using descriptive and inferential statistics. Result: In pre-test adolescent girls had poor knowledge score that is 17 (28%) and only 42(70%) adolescent girls showing moderate knowledge score and 1 (2%) adolescent girls are having good knowledge score. In post-test the majority of adolescent girls in post-test had good knowledge score that is 50(90%)) and 10(18%) adolescent girls showing average knowledge score. No samples are having poor knowledge score. Conclusion: It was concluded that post-test scores were more as compare to pre-test score thus adolescent girls has good knowledge score, thus the present study suggested that structured teaching programme on eating disorders was successful in gaining the knowledge of adolescent girls.