Over the last decade, 350,000 people have moved from Mongolia’s countryside to the suburbs of its capital, Ulaanbaatar, where they live in abject poverty despite the rapid economic development of the country. This article proposes three complementary international legal analyses of this internal migration. First, because this migration is partly and indirectly induced by the adverse impacts of climate change, States have a common but differentiated responsibility to assist the Mongolian government to address climate migration. Second, Mongolia should bear its own responsibilities to take steps to realize the social and economic rights of its population without discrimination. Third, Mongolia’s commercial partners should be warned against any control or influence that would cause harm to Mongolia, in application to public international law on State responsibility and to States’ extraterritorial human rights obligations. While each narrative reveals an important dimension of a complex phenomenon, this article argues that all policy levers must urgently be pulled to guarantee the rights of Mongolia’s internal migrants.