AbstractThis study examines the moderating role of project type between project delivery system (PDS) and cost performance to decide whether project types should be addressed prior to evaluating PDS performance. Previous studies evaluating PDSs performance using direct relationship analysis present controversial assessments in terms of cost-efficiency. They recognize that project type causes inconsistencies when comparing design–build (DB) and design–bid–build (DBB) systems. However, they have yet to determine the specific role of the project type, leading to ambiguity regarding how to control the project type (e.g., a dataset using unspecified or mixed project types). This study employed a moderation analysis to identify the role of project type and to compare the cost performance of DB and DBB systems associated with project types as a post hoc test, leveraging statistical methodology, based on 90 public building projects in Seoul, South Korea. The results show that the moderating effect of project type is statistically significant. The cost growth in DB for nonresidential building projects presents statistically lower than that in DBB, whereas the cost growth difference between DB and DBB for residential buildings is not statistically significant. Additional analysis of full life-cycle cost performance shows another dimension of comparison that indicates the cost performance comparison of DB and DBB projects is controversial and more likely to be influenced by other factors. This study contributes to the engineering in the management body of knowledge by distinguishing the effects of project type and PDS on cost performance using a causal relationship analysis. The findings provide objective criteria for public-sector practitioners in the Architecture, Engineering, and Construction industry on how to address project types when they evaluate and select PDS and enhance the consistency of PDS evaluation in terms of cost performance.