This article critically examined the role of Environmental Impact Assessment (EIA) law in advancing public participation and sustainable development in Nigeria and Scotland, highlighting their respective challenges and lessons. EIA serves as a crucial regulatory instrument for balancing developmental aspirations with environmental sustainability goals while providing a platform for participatory governance that ensures community perspectives are considered in decision-making. The study traces the historical evolution of EIA laws in both jurisdictions, with Nigeria enacting the Environmental Impact Assessment Act of 1992 and Scotland incorporating the European Union Directive 85/337/EEC, subsequently refined under the Town and Country Planning (Environmental Impact Assessment) (Scotland) Regulations 2017. Although both frameworks mandate public involvement, their effectiveness differs significantly due to varying socio-political, cultural, and institutional contexts. In Nigeria, weak enforcement, limited institutional capacity, political interference, and low levels of environmental literacy undermine the credibility and inclusiveness of EIA processes, rendering them often symbolic. Conversely, Scotland’s EIA system benefits from entrenched transparency, robust institutional frameworks, and a civic culture supportive of environmental governance, which enhance both accountability and sustainability outcomes. The comparative analysis reveals that effective implementation of EIA requires more than statutory provisions; it depends on institutional strength, public awareness, and mechanisms that ensure public input is meaningfully integrated into decision-making. The article concludes that Nigeria can learn from Scotland’s experience by enhancing institutional resources, simplifying technical reports, improving environmental education, and embedding accountability through judicial review, thereby transforming EIA law into a substantive tool for environmental justice, inclusive participation, and sustainable development