Adaptation to climate change is a critical issue in Southeast Asia. Academic and policy attention are increasing sharply as a result of the growing evidence on unavoidable impacts in the region. Southeast Asia is one of the most vulnerable regions to climatic hazards globally. Most, if not all, countries already are experiencing stresses from climate-related events and phenomena. The situation could be exacerbated by future climate change, which would lead to an increase in frequency and intensity of extreme events. Vulnerability to climatic hazards is expected to increase, especially in island states and countries with long coastlines and low-lying areas. The key vulnerable concerns encompass agriculture and food security, water resources, coastal zones and marine ecosystems, terrestrial ecosystems, human health, settlements, fisheries, and others. Already, initiatives have been carried out and planned in the regions, especially within national boundaries, to either reduce vulnerability or cope and adapt to future climatic hazards. However, there are several factors affecting adaptation in the regions. The constraints are wide-ranging and may differ in specific to country circumstances, encompassing methodological issues, biophysical limitations, socioeconomic factors, technological barriers, and institutional and technical aspects. More efforts are required to drive further responses, covering such aspects as vulnerability and adaptation assessments; methodology and approaches for modeling and data gathering; building of human and institutional capacity; financial and technical support; education, training and public awareness; and networking and information. Adaptation is a knowledge-intensive undertaking, which requires provision of access to relevant and usable knowledge to ensure effective implementation and outcome. There are a number of key priorities for the region in moving forward on adaptation responses, including improvement of data collection, management and dissemination; advancing integrated assessments covering biophysical and socioeconomic impacts as well as sectoral and cross-sectoral analysis; enhancement in the understanding of the relationship between climate change and disaster; and policy measures supporting implementation in an integrated and balanced manner.