Environmental constitutionalism – acknowledging that the environment and/or climate system are suitable subjects for recognition and protection within constitutional texts and for vindication by national courts – is increasingly seen as an idea ripe for development in Ireland. Momentum around environmental constitutionalism reached a peak in March 2023 when the Citizens’ Assembly on Biodiversity Loss recommended a referendum on inserting environmental and nature rights into Bunreacht na hÉireann. This article explores whether constitutionalising express environmental rights and/or duties could provide a transformative legal discourse for tackling the twin climate and biodiversity crises in Ireland.