Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique used to enhance local synaptic efficacy and modulate the electrical activity of the cortex in neurological disorders. Researchers have sought to combine this type of stimulation with well-established therapeutic modalities, such as motor training involving Xbox Kinect games, which has demonstrated promising results. Thus, this study aimed to determine whether tDCS can enhance upper limb motor training in an eight-year-old child with Down Syndrome (DS) (cognitive age: five years, based on the Wechsler Intelligence Scale for Children). The evaluations consisted of three-dimensional analysis of upper limb kinematics during a reaching task performed before, after10 session, and one month after the intervention. The intervention protocol involved 1 20-min sessions of tDCS over the primary motor cortex at an intensity of 1 mA during Xbox Kinect game training involving an upper limb motor task. The analysis of the kinematic data revealed that in the pre-intervention evaluation, the dominant limb executed the task slowly and over a long path. These aspects improved at the post-intervention and follow-up evaluations, as demonstrated by the shorter total movement duration (3.05 vs. 1.58 vs. 1.52 s, respectively). Similar changes occurred with the non-dominant upper limb; a significant increase in movement velocity at the post-intervention and follow-up evaluations was observed (0.53 vs. 0.54 vs. 0.85 m/s, respectively). The present case report offers preliminary data from a protocol study, and the results confirm the notion that anodal tDCS combined with upper limb motor training leads to improvements in different kinematic variables.