The aim of this study was to investigate the effects of fatigue and fatigue-related kinesiophobia on functional capacity, physical activity and quality of life in patients with Parkinson's disease. Twenty patients with Parkinson's disease were included in the study. The fatigue severity was assessed by the Fatigue Severity Scale, kinesiophobia by the Tampa Kinesiophobia Scale, functional capacity with the Six-Minute Walk Test, and quality of life was evaluated by the Parkinson's Disease Questionnaire. In addition, the physical activity level of each patient, such as the number of steps, active energy expenditure and total energy expenditure, were recorded for one week with an activity monitor mounted on the patients' arms. The mean age of the patients (10 female/10 male) was 69.85 +/- 9.38. According to the multiple regression analysis, a significant correlation was found between fatigue with 6-min walking test score (P = 0.039) and number of steps (P = 0.030). Also, a significant correlation was found between kinesiophobia with total energy expenditure (P = 0.013) and quality of life (P = 0.042). While fatigue was a significant determinant for functional capacity and number of steps, kinesiophobia was a significant determinant for total energy expenditure and quality of life. Fatigue and kinesiophobia are emphasized less compared to other findings in Parkinson's disease. However, fatigue and kinesiophobia symptoms negatively affect the functional capacity, physical activity and quality of life of patients. The results of this study revealed the need to evaluate fatigue and kinesiophobia, and the need to use physiotherapy and rehabilitation interventions to reduce these symptoms.