The literature on environmental impact assessments (EIA) tends to focus on national case studies, while neglecting subnational EIA systems. Federalist countries represent 40 % of the world’s population and by their design link national and subnational governments in institutional arrangements that delineate or share power across administrative and sectorial areas. Therefore, the study of institutional arrangements’ influence on the conduct of environmental policy such as EIA is important in evaluating its effectiveness. This research aims to contribute to this area by examining the national and subnational EIA systems in two federalist countries, Paraná, Brazil and California, United States (US). This involved a literature review of the scientific and grey literature as well as legislation and regulations of each case study. This analysis was organized along operational, legislative, administrative, and procedural characteristics building upon existing methods from the EIA literature. The results show each federal country presents different approaches to EIA policy. Brazil represents a more centralized top-down approach based on a licensing system, which offers broader coverage of projects and in theory more standardized implementation. In the case of Paraná, there has been a recent shift towards decentralizing the EIA process for smaller projects to municipalities, although there remain institutional and technical challenges. The US EIA system covers only public projects and therefore is considerably limited in its coverage. California presents the most institutionally and technically competent EIA system of those compared in this study. However, it still suffers from problems of inconsistent implementation and litigation abuse. All case studies are facing increasing political pressures to streamline their processes, often with the proposal of arbitrary timelines.