Through the lens of foreign policy, it is evident that China has profoundly accelerated and expanded its engagement in Southeast Asia, and that US regional policy has changed from inattention to proactive involvement as the US attempts to restrain China’s rise and maintain regional dominance. Increased US–China competition in Southeast Asia since the end of the Cold War generated a relatively favorable climate in which regional states could obtain economic, political, and security benefits. Therefore, Southeast Asian states were motivated to strategically advance their cooperation under ASEAN to maximize the benefits realized as a result of the advantageous international environment. The findings of foreign policy inquiry gain empirical support from statistical analysis which systematically compares the effects of US–China competition with those of the other variables, including joint ASEAN membership, joint degrees of democracy, and interstate conflict, suggesting that US–China competition has played a significant role in stimulating regional cooperation in Southeast Asia, particularly after the Cold War.