PurposeThe objectives of this paper are to examine the impact of psychological contract on project performance in private construction projects and to investigate if the positive effect of psychological contract on project performance can be mediated by inter-organisational teamwork.Design/methodology/approachMultiple regression analysis and mediation analysis were applied in this study to conduct the proposed hypotheses. Data were collected via questionnaire surveys from the construction professionals working for contractor firms on private construction projects.FindingsThe result of the multiple regression analysis indicated that psychological contract between contractors and owners is significantly related with project performance in construction projects. This study examined five psychological contract components, but the most important element was found as trust which can influence every aspect of project performance. Fairness is another key factor that can improve project performance in terms of budget and quality. Further, the findings of the mediation analysis revealed that inter-organisational teamwork has a mediating effect on the relationship between psychological contract and project performance.Originality/valueThis paper presents the important role of psychological contract between contractor and owner organizations in construction projects that can affect project performance. The study also highlights the significance of inter-organisational teamwork as a mediator to the relationship between psychological contract and project performance.