Children with suspected developmental disabilities often have handwriting difficulties and show problems with motor control of the head and upper limbs, but it has not been examined in detail. The purpose of this study was to examine the characteristics of motor control in children with suspected developmental disabilities and writing difficulties. Nineteen right-handed males who were receiving support in the resource room for handwriting difficulties (SDD group) were compared with 17 right-handed age-matched male controls. Both groups completed two handwriting tasks. The main measures were jerk and changes in joint angle, which were measured by a 3D motion analysis system. The SDD group had significantly higher mean values of jerk in the head, forearms, and hands and significantly greater changes in the joint angle of neck flexion in both handwriting tasks compared to the control group. Children with suspected developmental disabilities and handwriting difficulties had less smooth forearm movements and greater fixed head movements.