Abstract:- Background  of the study: Obesity is considered one of the growing health problems as it has great effects on the child and adolescent’s health; leading to significant health problems either organic or psychological. The aim of the study is to assess the knowledge regarding  physical activity on prevention of  obesity among adolescents girls. To assess the attitude regarding physical activity on prevention of obesity  among adolescents girls. To correlate the knowledge and attitude regarding physical activity on prevention of obesity among adolescents girls. To find out   the association between knowledge of   physical activity with their   selected  demographic variables. To find out   the association between   attitude   of   physical activity with their   selected  demographic variables. The research approach used for this study was quantitative approach. The research design for this study is Non experimental descriptive study design. Sample size was 100 adolescents  girls.  Convenient   sampling technique was used for the study. The collected data was analyzed by using both descriptive & inferential statistics. The study results found that out of  100 samples the majority of adolescents girls 67(67%) had inadequate knowledge, 23 (23%) had moderately adequate knowledge and 10 (10%) of students had adequate  level of knowledge regarding  physical activity on prevention of  obesity. Based on the attitude majority of the adolescents girls 56 ( 56%) had poor  attitude, 32 ( 32%) had good  attitude and 12 (12%) had very good attitude towards physical activity on prevention of  obesity. The overall knowledge mean score 53.77. The overall attitude mean score 39.2. There was a significant association found between the knowledge and age, education of mother, dietary pattern, hobbies. There was a significant association found between the   attitude and  education of mother, place of living. The study concluded that adolescents girls had inadequate knowledge and   poor attitude   regarding physical activity  on prevention of obesity…