The unprecedented economic growth in the 21th century could be largely attributed to a relatively peaceful international order following the collapse of the bipolar world order. However, contemporary populist backlash has threatened the international security, rendering the extant peace more and more fragile. This article aims to evaluate and explain certain threats posed by populism in the west, arguing that the populism, which challenges incumbent democratic regimes, economic globalization trend as well as various international institutions, is a serious threat to international order. A detailed explanation on the impact of populism, as exemplified by prominent leaders like Boris Johnson and Donald Trump, and by political events such as Brexit substantiates the article’s claims. In conclusion, the article argues that pan-West populism is on the rise, destabilizing current liberal governments and international institutions. Several policy recommendations are made to tackle the populist threats, such as reforming democratic procedures, implementing moderate redistribution policies, and rebalancing powers between international institutions and individual member countries.