This study examines how Brexit reshaped the institutional foundations of European Works Councils (EWCs). Using historical institutionalism, the analysis conceptualises Brexit as a critical juncture that revealed and accelerated existing institutional dynamics. Drawing on 64 company cases, including 16 in-depth studies, it identifies five developmental outcomes – stability, limitation, exclusion, extinction and innovation/expansion. Most EWCs maintained stability through negotiated adaptation, while others experienced limitations, exclusion or innovation. Outcomes were mainly influenced by management strategies and orientations, national employment relations systems and transnational employee coordination. The findings show how macro-level institutional disruptions translate into negotiated meso-level institutional recomposition.