Life style diseases are a part of the modern society. Obesity is rising in younger population in an alarming rate. The present study was conducted to assess the knowledge and attitude regarding prevention of obesity among adolescent girls in selected school. An evaluative approach was used with pre experimental one group pre test post test research design .A structured knowledge questionnaire and an attitude scale was used for data collection .A sample size of 100 was selected by non probability convenient sampling technique. The pretest was followed by the administration of SIM .Post test was done after 7 days. The study results showed that level of knowledge among adolescent girls was inadequate for 58%, 32% had moderate level of knowledge and only 5% had adequate .While considering the attitude scores it was revealed that 32% had unfavorable attitude ,54% had moderate and 14% had favorable attitude towards prevention of obesity .In the post test none of the adolescent girls had inadequate knowledge and 68% had adequate knowledge and 42 % had moderate level knowledge .There was improvement in the attitude level by 73% had favorable attitude and 37 had moderately favorable attitude scores after post test. The statistical association was calculated for knowledge score as well as attitude scores with selected demographic variables of adolescent girls and both were found to be non–significant .The study concluded that there is a need for teaching strategies for adolescent population to improve their knowledge and attitude level regarding life style diseases .