Relations between China and North Korea have gone through two distinct phases: from 2011 to 2018 relations were cool, characterized by a limited engagement of diplomatic personnel, an absence of high-level meetings, and the continued implementation of UN sanctions; in March 2018, however, there was a dramatic turning point, and from this point to the time of writing, relations have drastically improved. Kim Jong-un has visited China on multiple occasions and engaged in high-level meetings; there have been visits of Chinese personnel to North Korea and increased trade across the border into North Korea. This chapter surveys the historic relationship between China and North Korea, making the argument that contrary to popular and largely Western assumptions, the relationship has never been straightforward. Instead, it has been punctuated with periods of closeness and periods of greater estrangement. Understanding this history, and especially its ebbs and flows, is vital in seeking to understand China’s policy preferences, but also in developing strategies to respond to the security challenges emanating from North Korea.