The Taiwan crisis is one of the central geopolitical variables in the strategic rivalry between the People’s Republic of China (hereafter, China) and the United States. Its implications are not confined to bilateral relations between Beijing and Washington, but extend to the security, economy, and geostrategic dynamics of surrounding regions. Southeast Asia, due to its geopolitical position, geoeconomic significance, connection to vital maritime trade routes, and growing role in global supply chains, is directly affected by escalating tensions in the Taiwan Strait. Drawing on Regional Security Complex Theory and using a descriptive-analytical method, this article asks how Sino-American rivalry over Taiwan affects Southeast Asian regional security. It argues that the Taiwan crisis creates geoeconomic opportunities for strengthening Southeast Asia’s role in global supply chains while also increasing strategic uncertainty, the risk of disruption in the Strait of Malacca, threat perceptions of China, military expenditures, and tendencies toward new security coalitions. The findings show that the Taiwan crisis has a dual character for Southeast Asia: it generates economic opportunities while simultaneously increasing security and geopolitical risks.