How do Chinese national identity narratives affect Sino-South Korean relations? The Koguryo history war more than a decade ago was a turning point in bilateral relations since diplomatic normalization in 1992, generating enduring competition over representations of history.1 In 2010, China’s commemoration of its entry into the Korean War raised early warnings in South Korea over Beijing’s hostile foreign policy orientation under Xi Jinping. Contrary to such expectations, however, the earliest summit agreements between presidents Xi Jinping and Park Geun-hye after both took office in 2013 were on history cooperation as common victims of Japanese colonialism. Most notably in 2015, Park’s participation in Beijing’s 70th anniversary celebrations of the end of World War II consolidated joint claims of what was called the best period in bilateral relations.2 This chapter assesses the impact of Chinese national identity on China-Republic of Korea (ROK) relations under the Xi and Park administrations since 2013. It examines Chinese constructions of national identity and their implications for the security, economic, and cultural dimensions of the Sino-South Korean relationship. Rather than promoting partnership, competing identities across these dimensions reinforce enduring differences over the region’s political, economic, and cultural order. These differences surfaced most saliently in 2016, following an initial period of engagement that corresponds with the downward trend in China-Japan relations since 2012. Managing them requires the very trust-building that both Beijing and Seoul have prioritized since 2013.