Background: Public parks are increasingly recognized as important places that facilitate physical activity. Despite the presence of parks, constraints to recreation and physical activity at parks exist. As the health benefits identified with physical activity require long-term and regular activity, it is important to examine factors pertaining to physical activity participation beyond initiation. This study explored differences in reported constraints to park based physical activity and negotiation strategies by physical activity stage of change. Methods: Data were collected among visitors to one Minnesota state park via onsite and follow-up questionnaires. Results: The average visitor had a healthier weight than the average U.S. and Minnesota adult and the majority of visitors were meeting the physical activity recommendations (86.4%). Respondents in the inactive/ insufficient stages were more constrained and used fewer negotiation strategies than respondents in the maintenance stage. Conclusions: Results both support and expand on previous research findings. Specifically, this study supports research which indicates the adoption and maintenance of physical activity are influenced by different individual, social and environmental factors, and expands the research base by examining constraints and negotiation at different physical activity stages in a park setting. Implications of these findings provide directions for future stage-based intervention efforts.