This study aims to examine the role of Relational Stakeholder Management (RSM) on the success of sustainable construction projects in urban areas of Pakistan. The study also examines the mediating role of trust (competence trust, integrity trust, and intuitive trust) and the moderating role of project managers’ leadership skills. Data were collected from 303 professionals working on sustainable construction projects in Pakistan and analyzed using Structural Equation Modeling (SEM). The results show that RSM has a positive and significant direct impact on the success of sustainable construction projects, while competence trust and integrity trust mediate this relationship. However, Intuitive Trust did not mediate the relationship between RSM and project success. Furthermore, the project manager’s leadership competencies strengthen relationships with relational stakeholders and foster trust, thereby improving overall project success. This research highlights that, in addition to technical factors, human and relational aspects are crucial to the success of energy-efficient and low-carbon construction projects in urban areas of Pakistan. The study provides integrated empirical evidence on the interplay between stakeholder relationships, trust, and leadership, specifically in the context of sustainable construction projects in urban areas of Pakistan. The findings of the study provide practical insights to improve RSM, develop trust, and strengthen leadership competencies to enhance success in sustainable construction projects.