With a population of 1.43 billion people, one-third of whom live in poverty, the South Asia developing member countries (DMCs) of the Asian Development Bank (ADB) face the challenge of achieving and sustaining rapid economic growth to reduce poverty and attain other Millennium Development Goals in an era of accentuated risks posed by global climate change. Economic losses in key sectors, such as agriculture, energy, transport, health, water, coastal and marine, and tourism, are expected to be significant, rendering growth targets harder to achieve. This report synthesizes the results of country and sector studies on the economic costs and benefits of unilateral and regional actions on climate change in ADB’s six South Asia DMCs, namely Bangladesh, Bhutan, India, the Maldives, Nepal, and Sri Lanka. The study takes into account the different scenarios and impacts projected across vulnerable sectors and estimates the total economic loss throughout the 21st century and amount of funding required for adaptation measures to avert such potential losses. It is envisioned to strengthen decision-making capacities and improve understanding of the economics of climate change for the countries in South Asia.