governance, innovation, and performance, evidence from a longitudinal case study

Purpose This study investigates the long-term evolution of the Project Management Office (PMO) within the foundation of Organizational Project Management (OPM). It examines how the PMO'smandate, authority, and responsibilities developed in a large European organization, tracing its transition from departmental support to strategic governance and, more recently, to a central role in innovation and artificial intelligence (AI) initiatives. Design/methodology/approach A longitudinal single-case study design was employed, combining semi-structured interviews, internal documentation, and a follow-up questionnaire with Enterprise PMO (EPMO) professionals to identify PMO functions across stages and analyze mandate and authority expansion. Findings Three main findings emerged. First, the PMO evolved through four stages, expanding from IT support to enterprise-wide governance. This followed a layered mandate logic, where foundational functions were retained while governance and strategic roles were progressively added. Second, a decisive transformation occurred when the PMO was relocated from IT to board-level reporting, expanding its autonomy, process performance, and strategic influence. Third, the PMO was explicitly mandated to lead innovation and AI initiatives, positioning it as both a governance body and a driver of digital transformation. Originality/value This study provides a rare longitudinal examination of PMO evolution in the context of OPM, addressing limited empirical evidence on sustained PMO development beyond early support and governance roles. It advances the concept of the layered mandate and offers guidance for structuring PMOs to sustain stability, expand authority, and assume responsibility for innovation and AI governance.