Abstract:Represented by owner contractor conflict, project conflict influences cost performance diversely in different project delivery systems, due to their differences in source of conflict, project attributes, and the internal/external environment of organization. Based on the interactionist view of conflict, this paper tested the relationship between the owner contractor conflict and cost performance in design bid build (DBB) and design build (DB) projects with 187 valid questionnaires. Hypotheses were tested by using correlation analysis and regression analysis. Results indicate that the owner contractor conflict in DBB projects influences the project cost performance with an inversed U shape, which means a moderate level of conflict can improve cost performance until a certain point beyond which the cost performance diminishes. However, the owner contractor conflict in DB projects mainly produces negative impact on the project cost performance rather than the functional outcomes.