Transnational and non-state threats including international organized crime, terrorism, illicit trafficking (in drugs, wildlife, humans, arms, etc.), piracy, infectious disease, and illegal migration flows are major concerns in Southeast Asia. This paper examines IPCC projections for climate change to the region and discusses possible impacts of these changes upon transnational security. Overall, climate change could increase potential vulnerability to various transnational security threats. Southeast Asian livelihood and social systems will be pressured, while state and civil society capacity will be strained. This will intensify existing vulnerabilities to non-state security threats and raise the overall level of vulnerability and risk to both human and state security. Predicted climate change impacts are also likely to strengthen or help revive sub-state networks that have traditionally responded to environmental change and pressure via violence, crime, smuggling, banditry, trafficking, terrorism, and other such activities. This will contribute to the evolution, expansion, and growth of “new” war fighting groups while raising overall vulnerability to non-state threats from local to global scales.