Newly discovered Soviet archival documents reveal a previously unknown protest by Czech construction workers in Mongolia in 1968. The workers, part of a team building a hospital in Ulaanbaatar, organized a demonstration outside the headquarters of the Mongolian Trade Union Federation due to shortages of building materials. The Soviet embassy in Ulaanbaatar urgently reported the incident to Moscow, identifying the involvement of Czechoslovakia, China, and the Soviet Union itself. The protest occurred amidst a period of strained relations between socialist countries, particularly due to China’s “Cultural Revolution.” A Soviet diplomat documented a meeting with a Czech worker who detailed the protest and the frustrations leading up to it. The reports suggest a level of dissent in Mongolia that was tightly controlled by the Mongolian People’s Revolutionary Party and the Ministry of Internal Affairs, raising questions about the extent of Soviet monitoring and influence within the country. This discovery represents a unique historical document challenging the narrative of unwavering socialist solidarity in Mongolia.