This article examines how the ASEAN is managing the quintessential security challenges of the 21st century, particularly China’s emergence as a regional power, its expansive territorial claim in the South China Sea, and the US–China strategic rivalry in the Indo-Pacific region. As an organization tackling these security concerns, the ASEAN lacks the essential mechanism for conflict resolution, operates through informal diplomacy and moral suasion, and relies on consensus in making decisions. As a result, China has effectively divided the association during the talks on the peaceful settlement of the South China Sea dispute. China is currently formulating with the ASEAN a Code of Conduct of Parties in the South China Sea. All the same, China has made sure that any future agreement with the ASEAN imposes no constraints on its expansionist moves in the contested waters, and contains provisions that benefit its interests in the long run. Meanwhile, US–China strategic competition has prompted the ASEAN to think of ways to deal with this potential security threat. However, the association has failed to come up with a common strategy. In conclusion, this article argues that China’s emergence as a regional power, its maritime expansion into the South China Sea, and the US–China geopolitical contest are testing both the capacity and the limits of the ASEAN in resolving these security issues.