: The Australia-Tuvalu FalepiliUnion Treaty is the world’s first bilateral agreement regarding climate migration, which is important to the Australia-New Zealand-Pacific region and to the international community. Through the perspectives of the nexus of migration and security and legal doctrinal analysis, this legal column critically reviews articles 3 (human mobility) and 4 (security and defence) of the Treaty and Australia’s recently adopted immigration regulations. It argues that the guiding principles underlying the Treaty are human security for Tuvaluan people and national security for Australia, which might not always be