With many Southeast Asian countries dependent on marine ecosystems for food security and livelihoods, particularly in coastal communities, they are at significant risk to the impacts of climate change. This cross-country analysis by WorldFish seeks to better understand the risks associated with climate change and assess the various adaptation and policy options available. The report examines the adaption approaches of four coastal communities, one each in Thailand and Indonesia, and two in the Philippines, each within the context of multiple hazards: typhoons and flooding, coastal erosion, and salt intrusion. A range of participatory techniques are employed in the study, including community hazard mapping and focus group discussions, as well as regression analysis to examine climate-related impacts and the behaviour of affected households and communities. The report provides primary empirical data and analysis, a cost effectiveness analysis of planned adaptation options, and the determinant of choice of autonomous adaptation strategies for each study sites, before presenting the results of the study. The results show that households in coastal communities are autonomously and simultaneously adapting and responding to a confluence of climate impacts, with regional and geographic variations reflecting the rational reactions of communities experiencing differing degrees of each impact. The greatest impact is felt on livelihoods, with foregone income often twice as high as loss and damage of assets (primarily due to low asset values of poor communities). Vulnerability measures of both consumption levels and exposure to incidents of vulnerability reveal that Palawan in the Philippines is the most vulnerable, followed by Thailand, Batangas (Philippines), and Indonesia. The cost effectiveness analysis of planned adaptation strategies show ecosystem-based approaches to be more cost effective than hard infrastructure projects, and that a greater emphasis should be placed on protecting livelihoods. Perceptions regarding the severity of climate change were found to influence the decision of communities to adapt. Finally, although no evidence was found to show planned adaptation crowds out private and autonomous adaptation, external sources of funds and social capital as a substitute for self-insurance and self-protection may present a moral hazard problem that requires further research.