This research study examines the rich legacy of vernacular architecture in Tamil Nadu, India, with an emphasis on its historical relevance, architectural features, and sustainable practices. Tamil Nadu's vernacular architecture has a wide spectrum of forms, from major Dravidian temples to simple the village houses. These structures provide not just functional needs, but also represent the communities' cultural identity and religious values. Furthermore, vernacular architecture in Tamil Nadu is highly sensitive to the local environment, with buildings planned to maximize natural ventilation, lighting, and thermal comfort. Traditional building materials like lime, timber, and terracotta are supplied locally, reducing environmental effects, and encouraging sustainability. Focusing on historical documents and academic research this study investigates the cultural, socioeconomic, and environmental influences that have impacted Tamil Nadu's vernacular architecture throughout the centuries. It also examines the current relevance of traditional architectural techniques in the context of growing urbanization and industrialization, highlighting the importance of maintaining and incorporating indigenous knowledge into sustainable development initiatives. Through case studies and comparative research, the article emphasizes the adaptability of Tamil Nadu's vernacular architecture, as well as its potential contributions to modern architectural discourse and sustainable design practices. Keywords- Vernacular, architecture, climate responsiveness, sustainability, Tamil Nadu, South India, courtyard, Chettinad.