PurposeAlthough the literature is clear on what comprises effective project stakeholder management, communication between key stakeholders and project managers is often ineffective. Research is silent on stakeholders' insufficient knowledge of project management terminology, which is a barrier for such effective communication. This paper aims to identify the project management concepts that key stakeholders should understand to improve effective communication.Design/methodology/approachThis paper employs a three-step research design. In the first step, based on threshold concept theory, the authors identify the key project management concepts through interviews with 20 project management practitioners, trainers and trainees. In the second step, the authors confirm the findings from the first step and identify effective approaches to enhance project stakeholders' communication through seven additional interviews with project stakeholders. In the third step, the authors construct a functional model of the research findings by employing a system-level modeling tool.FindingsThis research identifies five project management threshold concepts (TC) that are challenging for project stakeholders to understand (1) project benefits, (2) the iron triangle, (3) the critical path, (4) uncertainty and (5) project leadership. Following these knowledge barriers, the paper proposes unique approaches to develop effective project stakeholder communication.Originality/valueThis paper advances project stakeholder management research by identifying knowledge barriers and providing project managers with more effective approaches to better engage with their stakeholders.