Rapid industrialization has led to the outward development of cities, but it has also worsened environmental issues, expanding global interest in sustainable development. In particular, the concept of "Environmentally Sound and Sustainable Development (ESSD)," proposed during the 1992 UN Conference on Environment and Development in Rio de Janeiro, Brazil, encouraged a shift in awareness regarding human living environments. As a result, the qualitative improvement of residential areas and environmental soundness have emerged as key challenges. In line with this global trend, South Korea introduced the "Green Building Certification System" in 2001. This system aims to realize pleasant and healthy residential environments through energy conservation, resource efficiency, and the creation of ecological environments. This study analyzes the current status of green spaces and biological habitats within residential complexes in the Seoul metropolitan area and compares the ecological environment at the time of certification with current conditions. The results show that while some complexes have improved the quality of their ecological environments through systematic and continuous management, many others have experienced a decline in biodiversity and a deterioration in the function of green spaces due to factors such as a lack of management personnel, budget constraints, and insufficient expertise. Based on these findings, this study presents the following policy recommendations. First, the certification should not be limited to a one-time evaluation. A periodic re-certification system should be introduced to establish an institutional foundation for regularly reviewing maintenance levels. Second, in order to effectively maintain ecological components, a system should be established that either permanently deploys landscape and ecology professionals within each complex or outsources management to specialized companies. This will allow ecological spaces to function as more than just certification requirements—they should become key elements that enhance actual residential satisfaction. This study empirically demonstrates the importance of post-certification management and governance systems in enhancing the effectiveness of the Green Building Certification System. It aims to serve as a valuable foundation for future policy development and the management of residential complexes, contributing to sustainable urban and housing policies.