Parkinson's disease is a neurodegenerative disease that frequently results in memory disorders, cognitive decline and dementia. Previous studies have reported that plasminogen activator inhibitor-1 (PAI-1) serves an important role in cardiovascular disease risk, adiposity, insulin resistance and inflammation. However, the role of PAI-1 in diagnosis and prognosis of patients with Parkinson's disease following deep brain stimulation (DBS) has not reported, to the best of our knowledge. Therefore, the purpose of the present study was to investigate the clinical significance of PAI-1 in patients with Parkinson's disease. Plasma PAI-1 levels were measured in 102 patients with Parkinson's disease who underwent DBS. It was demonstrated that plasma PAI-1 levels were significantly increased in patients with Parkinson's disease compared with healthy individuals (P<0.01). Patients with Parkinson's disease received DBS presented significantly improved cognitive competence compared with controls (P<0.01). DBS significantly decreased plasma PAI-1 levels in patients with Parkinson's disease compared with controls (P<0.05). It was also observed that plasma PAI-1 levels were significantly negatively associated with cognitive function for patients with Parkinson's disease (P<0.01). In conclusion, these findings demonstrated that the degree of Parkinson's disease severity is positively associated with circulating levels of plasma PAI-1 levels, which suggests that PAI-1 may be a potential diagnostic and prognostic marker for patients with Parkinson's disease.