Physical activity is also defined as a bodily movement which is produced by skeletal muscles that require energy expenditure. The Daily physical activity can reduce the risk factors such as hypertension, coronary heart disease, and juvenile diabetes mellitus, improves functional health and weight control. Due to lack of physical activity, the children can become overweight or obese. To find the association of physical activity with flexibility in healthy, overweight and obese children. Non-experimental, observational study and 100 samples were taken based on inclusion criteria to find the association of physical activity on flexibility in normal, overweight, obese children, between the age group of 11 - 13 years by using physical activity questionnaire (PAQ-C), Body Mass Index in percentile and, sit and reach test as outcome measures. The study setting was Sree Sankara BalaVidhyalaya School. The physical activity questionnaire was given to them and asked to fill the (PAQ-C) questionnaire, and the flexibility of each child was checked by sit and reach test. The score of the questionnaire and sit and reach test value was recorded. The results showed that there was no significant association in physical activity and flexibility in overweight and obese children. Whereas the physical activity was low among obese children than healthy weight and overweight children, and the flexibility was low among healthy children.