Purpose - This cross-sectional study aimed to investigate the relationship between quality of life (QoL), physical activity (PA), diet and overweight status in children 11 to 15 years old. Study participants - Participants (N = 1,771) children with self-reported physical activity and QoL outcome data. Methods - Cross-sectional survey of four secondary schools, using the PedsQL and EQ-5D QoL instruments; the CAPANS physical activity instrument and a food intake screener questionnaire. Results - The correlational analysis indicates little or no relationship between self-reported QoL, BMI and moderate to vigorous PA. We found no statistically significant differences between the two groups of children, who achieved the recommended PA guidelines and those who did not, on any of the dimensions of the PedsQL and the EQ-5D utility score. Only on the EQ-5D VAS dimensions score was there a statistically significant difference. Children who self-reported a BMI of overweight to obese had significantly lower QoL on both dimensions of the EQ-5D and every dimension of the PedsQL apart from School functioning. Conclusion - Overall this study showed mixed results for pupils achieving the recommended targets for physical activity and diet and their relationship with QoL. Hence, further study into PA and diet and their effects on QoL is needed.