Parkinson’s disease (PD) is one of the most prevalent neurodegenerative disorders causing progressive disability that can be slowed but not halted by treatment. A recent report describes an improvement in PD symptoms after a plant-based diet. This study aims to evaluate the influences of a plant-based diet on motor and non-motor symptoms of Parkinson disease. In the study, PD patients who had been on omnivorous diet prior to the study were switched to a vegan-based diet for three months. The patients underwent an evaluation of their motor and non-motor PD symptoms before and 3 months after the switch to vegan diet using the following scales: unified Parkinson’s disease scale (UPDRS), Parkinson’s disease sleep scale (PDSS-2), Epworth sleepiness scale (ESS), Beck depression inventory, Parkinson’s disease questionnaire- 39 (PDQ 39), Parkinson’s disease questionnaire- 8 (PDQ 8) and Patient assessment of constipation quality of life (PAC QOL) scale. Data before and after the dietary switch were compared. After the 3 month of vegan diet there was an improvement in most of the motor and non-motor parameters in one patient and mixed results were obtained in 2 patients with an improvement in some of the symptoms and worsening of other motor parameters. The results present a complex influence of vegan diet on motor and non-motor symptoms of PD. Further studies are required to elucidate the effect of vegan diet on PD.