Childhood overweight and obesity and low levels of physical activity are highly prevalent and have negative effects on health. The aim of this study was to evaluate and compare physical activity patterns in overweight and obese children through objective (accelerometer) and subjective (the International Physical Activity Questionnaire [IPAQ]) measures and to evaluate the degree of concordance between these two measures. This study was carried out in 11 to 13-year-old children in five primary schools in south Navarre (Spain). Caltrac accelerometers and the self-administered IPAQ were used to measure physical activity levels. The results showed a lack of concordance between the measures used (r = 0.49; p < 0.001).