Sustainable building practices have become increasingly central to global conversations on climate resilience, environmental protection, and resource efficiency. In Nigeria, however, the rapid growth of the construction industry has resulted in substantial environmental impacts, including high energy consumption, waste generation, and degradation of ecological systems. This study critically examines the role of Nigeria’s legal frameworks in promoting sustainable building practices. It evaluates key legislation such as the National Environmental Standards and Regulations Enforcement Agency (NESREA) Act, Environmental Impact Assessment (EIA) Act, Harmful Waste Act, Urban and Regional Planning Act, and the National Building Code (NBC). Using qualitative analysis supported by case studies, policy documents, institutional reports, and comparative international models, the research identifies significant gaps in the country’s legal architecture. Findings reveal that although Nigeria possesses environmental and construction-related laws that theoretically support sustainable building principles, enforcement remains weak due to corruption, institutional fragmentation, insufficient technical capacity, and poor public awareness. Case analyses including the 2016 Lekki building collapse and Lagos State environmental reforms illustrate both regulatory failures and emerging opportunities. Comparative reviews from South Africa, India, and the United Kingdom demonstrate the importance of integrating sustainability standards into binding legislation, strengthening enforcement agencies, and coupling legal penalties with incentives. The study concludes that Nigeria must adopt a harmonized legal framework that merges environmental and construction laws, strengthens institutional capacity, mandates sustainability compliance through enforceable codes, and incentivizes green building adoption. Recommendations include NBC domestication across states, amendments to key legislation, introduction of green building incentives, and creation of a specialized Green Building Tribunal. Such reforms will significantly enhance sustainable building practices and environmental protection within Nigeria’s construction sector