This study aimed at Evaluating the socioeconomic status (SES), physical activity (PA), physical fitness and sedentary activity in Iranian children aged 7-11 years. We analysed the following cross-section data from a selected sample of children (N=766) aged 7 to 11 years: age, anthropometric characteristics, SES, PA, ten physical fitness tests and sedentary activities. 29.4% and 31.3% of the children reported TV watching and video playing daily time (TVVPT) higher than 3 and 4 hours/day, respectively. Fat mass (FM) was significantly related to PA (r=-0.165; P<0.01), cardiorespiratory fitness (CRF) (r=-0.793; P<0.01), and TVVPT (r=0.200; P<0.01), after controlling for age and SES. Although, the children by high-SES represented higher height, weight, body mass index, waist circumference, FM and fat free mass than the children by mid-SES and low-SES, but the differences were not significant among them. Although, PA was not different among the children by SES, however, the children by high-SES represented significant higher TVVPT than the children by mid-SES and low-SES (p<0.05); and had significant lower CRF than the children by mid-SES (p<0.05). The results of this study indicated higher sedentary activities and lower CRF in the children by high-SES in comparison to the children by mid-SES and low-SES. Furthermore, regarding the relationship between FM with PA, CRF and sedentary activity, increased PA and decreased sedentary behavior in children as much as possible should be considered.