This study investigated whether an association exists between irritable bowel syndrome (IBS) and the risk of Parkinson's disease. This is a retrospective cohort study using the dataset of the Taiwan National Health Insurance Program from 2000 to 2010. We identified 23,875 patients (aged 20 years or older) with newly diagnosed IBS as the IBS group and 95,500 subjects without IBS as the non-IBS group for comparison. The main outcome was incident Parkinson's disease compared between both groups by the end of 2010. We measured the hazard ratio (HR) to evaluate the association between IBS and Parkinson's disease. The overall incidence of Parkinson's disease in the IBS group was 1.76-fold higher than that in the non-IBS group (16.4 vs. 9.33 per 10,000 person-years). The multivariable Cox proportional hazards regression analysis revealed that the adjusted HR of Parkinson's disease associated with IBS was 1.48 (95% CI 1.27, 1.72), compared with the non-IBS group. Age, women, hypertension, dementia, cerebrovascular disease and depression were also significantly associated with Parkinson's disease. Patients with irritable bowel syndrome are at an increased risk of developing Parkinson's disease. Further studies are required to explore the pathophysiological connection between these disorders.