The role of North and South Korea in US–China relations remains a complicated one. Beijing and Washington share the goal of North Korea’s denuclearization yet achieving that objective is increasingly unlikely. In addition, the desire to keep Pyongyang from disturbing regional security through provocative actions is an additional challenge. While Washington regularly calls on China to do more to restrain North Korea, and some voices in China are making similar calls, there are limits to how far Beijing will press North Korea; stability is far more important to Beijing than denuclearization. North Korea will remain a serious flashpoint for conflict in the region and a major point of contact for US–China relations. South Korea is a different matter having become one of the world’s economic powerhouses, and since its founding, tied closely to its alliance relationship with the United States. In the years ahead, Seoul could be facing a strategic dilemma as China’s rise has been a huge economic opportunity for South Korea as it has for everyone in Asia. Should US–China relations worsen, South Korea could be in a difficult bind and would need to do yeoman’s work balancing these two relationships. In the end, North and South Korean roles in US–China relations are multifaceted, part challenge and part opportunity, and closely tied to the uncertainty that characterizes the Asia-Pacific.