Parkinson's disease (PD) is the second most common neurodegenerative disease, characterized pathologically by the progressive loss of dopaminergic neurons in the substantia nigra and clinically by the presence of motor symptoms such as bradykinesia, resting tremor, and/or rigidity. Among the motor deficits frequently observed in PD, patients are known to frequently report difficulties with manual dexterity. Many upper extremity and manual dexterity deficits are present in PD. Motor imagery (MI) is the imaginal execution of motor activities or the activation of specific muscles in the absence of any explicit feedback. This area of rehabilitation has been shown to be effective in improving and developing motor skills in many neurological conditions where patients exhibit motor recognition and execution impairments. MI can be applied at all stages of recovery from PD, is highly effective in movement-related pathologies, and can be performed independently.There is sufficient evidence that MI improves motor performance and learning in individuals with neurological disorders such as multiple sclerosis, stroke, and spinal cord injury. The study was designed to investigate the immediate effects of mental imagery, which is thought to be effective in controlling difficulties in planning and initiating movements in PD, on upper extremity skills. Therefore, the aim of this study was to determine the effect of mental imagery on upper extremity skills in PD.