Autism spectrum disorders and developmental coordination disorders are both associated with sensorimotor impairments, yet their nature and specificity remain unknown. In order to clearly distinguish the specificity between the two disorders, children with autism spectrum disorder or developmental coordination disorder presenting the same degree of motor impairment, thus homogeneous profiles, were examined in a reach-to-displace paradigm, which allows the integrity of two main aspects of motor control (anticipation/feedforward control and movement correction/feedback control) to be separately interrogated. We manipulated children's previous knowledge of the weight of the object they were to displace: when known, participants could anticipate the consequences of the weight when reaching for the object, prior to contact with it, thus allowing for feedforward control. Conversely, when unknown prior to contact, participants had to cope with the object weight in the displacing phase of the movement, and use feedback control. Results revealed a preserved feedforward control, but an impaired movement execution (atypical slowness) in children with developmental coordination disorder, while children with autism spectrum disorder displayed the opposite pattern with an impaired feedforward control, but a preserved feedback one. These findings shed light on how specific motor impairments might differently characterize developmental disorders and call for motor rehabilitation programmes adapted to each population.