The implementation of an ecosystem approach to fisheries (EAF) contributes to sustainable fisheries in various ways. One of them is by reviewing national policy and legal instruments to identify gaps, which prevent a country from progressing towards full alignment with, and implementation of, an EAF. This diagnostic tool builds on the previous work of FAO by translating the 17 EAF components identified in the How-to Guide on legislating for an EAF into an EAF Legal Checklist. A diagnostic tool for implementing an EAF through policy and legal frameworks were developed to help legal practitioners, policymakers and fisheries managers in assessing and implementing an EAF.