Diplomatic relationships with China had been the most crucial issue to Korean and Vietnamese Dynasties throughout history. Korean diplomacy has been well documented, yet the nature of Vietnamese activities are little known, even basic facts such as members of the missions, timing of departure/return, and their tasks in China. Since Korean and Vietnamese missions used Chinese characters as their official letters, there were cultural exchanges among them, especially poem recitation, in the capitals of Chinese Dynasties as a by-product of their diplomacy toward China. It has been found that around 20 cases of such exchanges had taken place from 14th through to 18th centuries. Relationships between Korea/Vietnam and China showed occasional changes, reflecting the times. This paper discusses the cultural and historical significance of the exchanges of Korean and Vietnamese diplomatic missions that occurred in Beijing, a foreign capital.