Purpose <p>Sustainable delivery of public infrastructure projects is increasingly challenged by systemic risks, resource constraints, and persistent supply chain disruptions. This study investigates how project mitigation strategies and project characteristics contribute to sustainable project outcomes and risk reduction in public infrastructure projects, while examining the moderating role of supply chain disruptions. By integrating internal project practices with external uncertainty, the study responds to growing calls for resilience-oriented and sustainability-focused project management frameworks.</p> Method <p>A quantitative, cross-sectional research design was employed, utilizing data collected from 300 professionals working on Saudi public infrastructure projects, including project managers, planning engineers, procurement officers, and government sponsors. Validated scales adapted from prior studies measured mitigation strategies, project characteristics, supply chain disruptions, project outcomes and risk reduction. Data were analyzed using Stata through confirmatory factor analysis and structural equation modeling to test direct and moderating hypotheses.</p> Findings <p>The results indicate that mitigation strategies and project characteristics have significant positive effects on project outcomes and risk reduction, supporting their role in enhancing sustainable infrastructure performance. Supply chain disruptions significantly moderate these relationships, weakening the effectiveness of mitigation strategies while amplifying the influence of inherent project characteristics under high disruption conditions. The model demonstrates strong explanatory power, confirming that external uncertainties critically shape the sustainability and resilience of infrastructure project delivery.</p> Originality/implications <p>This study contributes to sustainability research by integrating risk mitigation, project structure, and supply chain resilience into a single empirical framework grounded in contingency theory. Practically, the findings highlight the necessity for adaptive, context-sensitive, and resilience-oriented project management approaches to support sustainable infrastructure development. The results offer actionable insights for policymakers and practitioners seeking to strengthen infrastructure systems in line with long-term sustainability goals and Sustainable Development Goal 9 (Industry, Innovation and Infrastructure).</p>