This study was planned to determine the effects of school-based exercise practices (SBEP) on obesity and health-related quality of life (HRQL) in 9-11 year old girls. Participants consist of girls students from 9-11 years old in two state schools in Kars. Intervention Group (n: 85) courses of games and physical activities (CGPA) and SBEP (Basketball, Handball, Volleyball, Badminton, Table Tennis) and Control Group (n: 85) were formed as only CGPA. The exercise program; intervention groups was made subject to a training load of 60-70% and repetitions making up 3 days a week for 60 minutes a day, whereas the control group is a compulsory lesson 45 minutes three days a week in the gym or playground. Health-Related Quality of Life Scale (Kid-KINDL) was used in order to define the girl student quality of life before and after SBEP while Exercise Self-Efficacy Scale (ESS) was used for determining their exercise levels. According to the findings; Intervention group was found to be significant at p<0.001 level according to the height, weight and body mass index control group of girl students. 4 months after intervention, the proportion of obesity in the intervention group was 25.2% and the rate of overweight was 14.2% while it was observed that the control group had a statistically insignificant decrease in BMI. Intervention group's scores of sub-dimensions of total quality of life, physical well-being, emotional well-being, self-esteem, family as well as exercise self-efficacy levels (ESL) were observed significantly high (p<0.001) compared to control group. A positive relationship (p<0.01; p<0.05) at the level of r = 0.361; r = 0.305; r = 0.219 was found between ESL and the sub-dimensions of physical well-being, emotional well-being and self-esteem of HRQL of intervention group while a significant relationship (p<0.05) at the level of r = 0.230 was determined between ESL and the sub-dimension of friends of HRQL Scale of control group. Consequently, Female students have a positive effect on ESL and HRQL. Obesity rate decreases as ESL increases and HRQL levels also increase significantly. SBEP participation should be increased at the point of increasing HRQL in children's daily lives and educational settings.