This article takes stock of the contribution of the International Tribunal for the Lawof the Sea (ITLOS) to the development of international environmental law. It examines in this regard the jurisdiction of the tribunal and provides an overview of its environmental jurisprudence. It then assesses the potential role of ITLOS in relation to some marine environmental challenges ahead. In particular, it con-siders the possibility of a request for an advisory opinion on climate change, the settlement of disputes regarding deep sea-bed mining, and the potential role of the tribunal under a new legal instrument on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction