Background: in recent years the prevalence of obesity in infants, children, and adolescents has increased alarmingly, which may affect their health, educational level, and quality of life. Objectives: the aim of this study was to determine whether a program with physical activity and nutritional recommendations may improve health-related quality of life (HRQL) in overweight and obese children. Material and methods: the design of this study was that of a randomized clinical trial (RCT). The sample consisted of 54 children with a median age of 10.65 years, all of them overweight or obese. They were divided into a study (SG) and a control (CG) group, with 27 children each. The study group received physical activity and nutritional advice, while the control group only received theoretical-practical sessions on nutrition during 9 months. Families participated in the workshops on nutritional recommendations in both groups. Results: there was a significant difference in fat percentage before and after the intervention in the study group compared to the children who did not engage in sports activity. In the SF-10 quality-of-life perception questionnaire, statistically significant differences in both the physical and mental components may be seen at the end of the study between both groups (p < 0.001). Conclusions: an educational intervention with physical activity based on play and nutritional advice improved quality of life in overweight and obese children. Family involvement is vital for children to improve their life habits, and achieve favorable results in the reduction of overweight and obesity.