Implementing infrastructure development projects using public–private partnership (PPP) delivery method has not been widely successful, particularly in developing countries such as Iran. Therefore, it is essential and indispensable to evaluate the critical success factors (CSFs) for completing abandoned public sports facilities projects (APSFPs) via private sector participation under the PPP model. The current study aims to determine the CSFs for private sector participation in completing APSFPs based in Iran. The significance of this study stems from the criticality of deciding on CSFs as the first step of providing an appropriate platform for completing APSFPs in developing countries, including Iran, and encouraging more successful implementation in practice. This research promotes strategic thinking about PPP strategy and the effective use of resources by identifying CSFs required for completing APSFPs with success. To achieve the research objective, the Delphi survey method was applied to identify CSFs for private sector participation in completing APSFPs in Iran. The hands-on opinions of 10 experts in public sports facilities projects were gathered through three Delphi rounds of survey using a semi-structured questionnaire. The reliability and face, content, and structural validity of the questionnaire were also investigated and checked. A total of 20 CSFs for completion of APSFPs through private sector participation in Iran were determined and analyzed. The identified CSFs were further grouped into five different major factor categories: legal and regulatory, strategic/executive, political/cultural/social, process/structural/human and economic/financial. The findings of this study suggest that practical effective strategies or pragmatic measures need to be developed to enhance the successful completion of APSFPs in Iran and other developing countries under the PPP delivery model.