Government-sponsored public–private partnership (PPP) projects in the United Kingdom face particular complexity and uncertainty challenges because of the country’s specific socioeconomic context. This research investigates the role of governance and stakeholder management in PPP-based sustainable projects by conducting a mixed methods approach, which includes a quantitative survey and a qualitative case study inference. The results show that project governance and stakeholder management have a significant positive impact toward sustainable development and PPP project success. Whereas the negative impact of opportunism over contractual governance and stakeholder management is insignificant. Similarly, the negative effect of project uncertainty over contractual governance is insignificant toward sustainable development.