Obesity is a serious health problem and its prevalence has increased dramatically over the past 20 years. The proportion of children and adolescents who are overweight and obese have also been increasing. The magnitude of overweight ranges from 9% to 27.5% and obesity ranges from 1% to 12.9% among Indian children. A descriptive study was conducted, to assess the knowledge regarding obesity and its ill- effect among adolescent girls. 30 adolescent girls those who were studying in the b.sc fourth year of Bombay Hospital College of Nursing Indore were selected by non-probability purposive sampling technique. The demographic data revealed that 83.33%(25) of adolescents were in 21 years,73.33%(22) of adolescents were above 51Kg in weight, 90% (27) adolescents were more than151cm in height. The data was collected through structured knowledge questionnaires. The findings showed that 63.33% (19) adolescent girls had an average knowledge and 26.66% (8) adolescent girls had good knowledge regarding obesity and its ill- effect on health. This study concluded that adolescent girls should be provided with adequate knowledge and awareness regarding obesity and its ill- effect on health. Based on the findings health education programmes can be conducted to bring more awareness among adolescent girls to decrease the risk of obesity-associated ill- effects on health.