Climate-induced migration has emerged as a critical challenge to national security and regional stability in South Asia, one of the world’s most climate-vulnerable and geopolitically tense regions. This chapter explores how environmental displacement, driven by floods, sea-level rise, and extreme weather causes deep-rooted political, ethnic, and territorial tensions, particularly in Bangladesh, India, and Pakistan. It argues that climate migration acts as a threat multiplier, exacerbating resource scarcity, inflaming identity-based conflicts, and straining state capacity. As cross-border movements intensify, they are increasingly framed as security threats, leading to border militarization, antimigrant sentiments, and hostile policy shifts. This chapter critically assesses the security and geopolitical implications of climate migration, while highlighting the failures of regional mechanisms such as SAARC (South Asian Association for Regional Cooperation) to facilitate cooperative responses. Drawing on extensive empirical data and expert interviews, it calls for an integrated, human-centered, and regionally coordinated framework to mitigate climate-induced security threats in South Asia.