This paper investigates the stakeholder analysis and engagement in the field of project management. In response to the limits of prior studies, we propose a relevant conceptual approach by moving from a stakeholder relational perspective, anchored in recent studies on Social Network Theory, to a stakeholder relational ontology, anchored in Actor-Network Theory (ANT). We apply our approach to read and understand a longitudinal case study of an Information System (IS) project. Our most important findings suggest that this approach based on ANT improves stakeholders' analysis of and engagement in a project by shedding light on the dynamic and emergent nature of the relationships, since we demonstrate that the nature, roles, and relations between stakeholders co-evolve with the project's definition and trajectory. Consequently, we can provide project managers with a relevant approach that informs them about what to observe in stakeholder project networks, as well as how and when to observe them.