Objective: The purpose of this study was to explore how the functional impact of Parkinson's disease affects participation and to evaluate whether positive psychological capital (PsyCap) mediates the relationship within the context of the World Health Organization International Classification of Functioning, Disability, and Health Model. Method: Survey responses were analyzed from 144 adults with Parkinson's disease using a quantitative, correlational research design employing multiple regression and hierarchical regression analysis to examine hypothesized relationships. Results: The results of the correlation analysis indicated that there was a statistically significant, moderate-to-strong positive correlation between functioning and PsyCap and participation. Hierarchical regression analysis revealed that functioning accounted for 65% of the variance in participation. Although PsyCap was associated with participation, no mediating effect was observed. Conclusions: The results are consistent with traditional clinical judgment that physical functioning is positively correlated with participation. This study represents the first evaluation of the role of PsyCap in people with Parkinson's disease, and the results of the correlational analysis suggest that continued investigation of these relationships is warranted. Background: Parkinson's disease results in a variety of motor and non-motor features that frequently result in reduced participation in valued life activities.