Purpose The purpose of this paper is to identify and prioritize key performance indicators (KPIs) that can be used for stage-based performance assessment of build-operate-transfer (BOT) projects. Design/methodology/approach This research was conducted through focus group discussions and face-to-face questionnaires. Firstly, stage-level KPIs for BOT projects were identified by conducting a literature survey. The list of KPIs that can be used for measuring performance at different stages of a BOT project was finalized by conducting focus group discussions with 12 participants. The data related to the importance of identified KPIs were collected via a face-to-face questionnaire in which 30 high-level managers participated. Based on these data, KPIs were prioritized considering eight different stages of a BOT project by using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). Findings The research findings reveal that 63 stage-level KPIs can be used for measuring the performance of BOT projects at eight different stages, which are "feasibility study and preliminary plan," "announcement and submission of application," "evaluation and selection," "negotiation and signing of concession agreement," "design," "construction," "operation" and "transfer." The most important KPIs were determined as "comprehensiveness of project technical feasibility," "detailed tendering procedure," "effectiveness of concessionaires' technical knowledge/capability evaluation," "good relationships between government and concessionaire," "technology transfer," "effectiveness of quality control," "effectiveness of facility management" and "effectiveness of hand-back management" for each stage. The findings can be used by companies to evaluate performance at each stage of a BOT project and, if necessary, take the necessary actions for performance improvement at the stage level. Research limitations/implications The main limitation is the size of the sample, which represents the perspectives of 30 Turkish high-level managers on KPIs in BOT projects. Besides, the selected method, namely, TOPSIS, does not provide quality measures related to the outputs; therefore, it is difficult to see the inconsistencies among the experts. Practical implications The study findings will help in devising appropriate performance evaluation practices for BOT projects to overcome the shortfalls of the existing practices and systems proposed in the literature and help in achieving the superior performance while developing infrastructure through the BOT route. Originality/value This paper proposes a process-based approach for measuring the performance of a BOT project considering eight different stages. It fills a research gap in the public-private partnership literature by focusing on stages rather than phases. The results can be used by practitioners to establish stage-level performance management systems for BOT projects.