One of the most significant threats to environmental sustainability in the twenty-first century is fast-paced urban growth. The ecological degradation is particularly acute in eco-sensitive zones (ESZs) due to increasing urbanization, infrastructure development, industrialization and population pressure. Eco-sensitive zones are environmentally sensitive areas around protected forests, wildlife sanctuaries, national parks, wetlands and bio-diversity hotspots which need to have regulated development to maintain ecological balance. In India, urban activities are increasingly encroaching upon such regions, resulting in deforestation, habitat fragmentation, loss of biodiversity, pollution and climate-related vulnerabilities. This paper critically examines the relationship between urban expansion and ecological fragility with special emphasis on the legal and regulatory framework governing cities located within or around eco-sensitive zones. The doctrinal and analytical research methodology is used for the study based on statutes, judicial decisions, policy reports, government notifications and scholastic literature. The paper analyses the constitutional bases of environment protection under Articles 21, 48A and 51A(g) of the Constitution of India and statutory mechanisms such as the Environment (Protection) Act, 1986, the Wildlife Protection Act, 1972 and the National Green Tribunal Act, 2010. The role of the Ministry of Environment, Forest and Climate Change (MoEFCC), judicial interventions by the Supreme Court and National Green Tribunal and the implementation challenges of eco-sensitive zone notifications are also discussed. The findings reveal that despite a large environmental legal framework in India, poor enforcement, administrative conflicts, political pressure and economic interests often undermine ecological protection. Urbanization in ecologically sensitive areas has often been done without suitable environmental impact assessments and without adhering to zoning laws. The study further underscores the conflict between developmental ambitions and environmental conservation and emphasizes the importance of sustainable urban governance. The paper concludes that integrated urban planning, strengthening of environmental compliance mechanisms, community participation, scientific monitoring and judicial accountability are the key to effective regulation of cities in eco-sensitive zones. To achieve sustainable development, we need to strike a balance between urban development and the preservation of ecology. The recommendation of the study includes strict land use regulation, mapping of ecological impacts, decentralized governance of the environment, and increased public awareness in order to achieve long-term environmental security and intergenerational equity.