Stress can transiently increase motor symptoms of Parkinson's disease (PD), but it is unclear whether other behavioural changes associated with PD are also affected. We found that reaching-grasping was impaired in 19 PD patients compared with 19 matched controls, but these impairments were not amplified by stress. However, patients showed a stress-induced reduction of hedonic responses. Stress may amplify those impairments in PD that are not accessible to cognitive control.