The article discusses three diaries written by the Russian diplomat G.A. Planson (1859-1948) during his service in Korea as Russian Consul General in Seoul (1905-1908). At present, the diaries are kept in the collection of the GARF archive (Moscow). Chronologically, they cover the period from June 25, 1906 to August 9, 1908. During this period, the Russian Empire showed a stable military-strategic and financial interest in the Far East, in particular, in Korea, but its influence in the region was declining. In contrast to the Japanese influence, which systematically increased in Korea during this historical period. The diary entries contain reflections on Korea and Russian-Korean relations; plots from private life (the search for a servant to Sergei (son of G.A. Planson) to accompany him to Russian posts and the related attempts to infiltrate the territory of the Russian Empire by Japanese spies); notes on the attitude of the Japanese towards Europeans and Americans (Attack of Japanese soldiers on the French Bishop Mutel in a Catholic cathedral; ban on congratulating Americans on the occasion of US Independence Day); embarrassment associated with the transfer of diplomatic correspondence (Transfer of personal values as a guarantor of the authenticity of the letter). G.A. Planson met several times with Korean Resident General Ito Hirobumi (1841-1909), Nikolas of Japan (1836-1912), about which he also left notes in his diaries. The diplomat's notes are valuable for information about private events that took place in Korea in the first decade of the 20th century. This information makes it possible to supplement the historical picture of the specified period and look at well-known events through the prism of the perception of a Russian diplomat.