Many governments face the problem of IUU fishing. Spain is a state party to the United Nations Convention on the Law of the Sea (UNCLOS) and has comprehensive spatial planning compatible with international norms. In its maritime territory, the penal code is applied according to the legal regime applicable the different areas and within limitations imposed by international law. Based on this scenario, the sanctioning of IUU fishing will be conditioned by material, spatial, national and jurisdictional aspects. The aim of this article is to study the criminal prosecution and sanctioning of IUU fishing in waters under Spanish sovereignty and/or jurisdiction from a critical perspective, in the light of public international law.