Sustainability is an imperative goal for developing public-private partnership (PPP) projects, which are largely affected by policies. However, few studies have explored the impact of policy implementation on the sustainable development of PPP projects. This study examines the impacts of PPP policy implementation on PPP sustainability by conducting a comprehensive analysis that is grounded in a proposed stakeholder-based framework of the PPP policy implementation process. Critical factors are identified through exploratory factor analysis (EFA) of 275 survey responses from PPP practitioners in China. Subsequently, ordinary least squares (OLS) regression analysis is used to examine the effects of policy implementation on project sustainability in PPPs. The results reveal five factors that can explain the construct of PPP policy implementation, namely, the implementing organization's capacity (F1), policy quality and resources (F2), the environment (F3), the involvement of the target group (F4), and the sustainability of the PPP projects (F5). F1, F3, and F4 have significant positive impacts on PPP sustainability, which is measured in terms of its economic, social, and environmental dimensions.