In addition to the core symptoms defining ADHD, affected children often experience motor problems; in particular, graphomotor movements including handwriting are affected. However, in clinical settings, there is little emphasis on standardized and objective diagnosing and treatment of those difficulties. The present study investigated for the first time the effects of methylphenidate as well as physiotherapeutic treatment on objectively assessed graphomotor movements compared to a control condition, i.e. parental psychoeducation, in 58 children (mean age: 9.52 ± 1.91 years) newly diagnosed with ADHD in an outpatient clinic for child and adolescent psychiatry. Families were invited to join one of the treatment groups. Before and after 8 weeks of treatment, children performed six different tasks on a digitizing tablet which allowed the objective analysis of three important kinematic parameters of graphomotor movements (fluency, velocity, and pen pressure) in different levels of visual control and automation. Graphomotor movement fluency and velocity improves over time across the groups, especially in tasks with eyes closed. We did not find clear evidence for beneficial effects of methylphenidate or physiotherapeutic treatment on children’s overall graphomotor movements suggesting that treatments need to be better tailored towards specific and individual deficits in graphomotor movements.