Children with developmental language disorders (DLD) often experience difficulty in understanding and engaging in interactive behavior with other children, which may lead to reduced daily physical activity and fitness levels. The present study evaluated the physical activity and physical fitness levels of 8–11 year old children with DLD (n =27) and compared this to typically developing (TD) age and gender matched controls (n =27). In addition, it was investigated whether interrelationships existed between physical activity and physical fitness in children with DLD and in TD children. Physical activity was measured using accelerometers. Physical fitness was measured using five tests of the Eurofit test battery (standing broad jump (SBJ), sit-ups (SUP), handgrip (HG), 10×5m shuttle run (10×5m SR), and the 20m shuttle run test (20m SR)). Physical activity of children with DLD did not significantly differ from TD children. Physical fitness of children with DLD was significantly lower on the SBJ, SUP, HG and 10×5m SR than TD controls, while no significant difference was found on the 20m SR. Strong significant relationships were found between physical activity variables and sedentary behavior and some physical fitness measures (SBJ and SUP) in children with DLD, while in TD children a strong significant relationship was found between time spent in moderate to vigorous physical activity and performance on the SBJ. This study reveals important differences in fitness between children with DLD and TD children, which should be taken into account when creating physical activity interventions. Special attention has to be paid to children with DLD who show low physical activity and low physical fitness performance.