Previous research has found improvements in motor control following Assisted Cycle Therapy (ACT) in persons with Parkinson's disease, Down syndrome (DS) and autism. Our study examined the effect of ACT on manual dexterity in adults with Attention Deficit Hyperactivity Disorder (ADHD). Nine adults with ADHD completed six weeks of light intensity cycling on a stationary bicycle, three times per week for 30 minutes. Four adults with ADHD were in the voluntary cycling (VC) group in which they pedaled at their self-selected rate. Five adults with ADHD were in the ACT group in which a motor moved their legs at a rate approximately 13% faster than their voluntary rate. Our results showed that the dominant hand moved more pegs following ACT than VC. Our results were interpreted with respect to upregulation of neurotrophic factors in the motor cortex following ACT.