Purpose ‐ The paper aims to develop a project success index (PSI) to benchmark the performance of design-build projects from a number of key performance indicators (KPIs). Design/methodology/approach ‐ This research collected 92 responses from Design and Build (D&B) project participants of the Hong Kong construction industry via ordinary postal mail. In addition, a project success equation is formulated from the principal components analysis. Findings ‐ D&B project participants suggests that time, cost, quality and functionality should be the principal success criteria for D&B projects. A single index can also be computed from the project success equation to apply different weightings to the respective KPI with different significance. Practical implications ‐ The concept of success remains vague among project participants, which makes it difficult to assess whether the performance of a project is a success or failure. The development of PSI can quantify the success concept in a scientific manner. Originality/value ‐ PSI indicates the success level of a construction project for benchmarking purposes. It also enables project stakeholders to measure the success of a D&B project and to compare the relative success level among different D&B projects in a scientific manner.