Tunkin was a graduate of the Institute of State and Law, Moscow (1935) and conducted post-graduate study at the same Institute from 1935-1938.
From 1939 to 1941, he was the Assistant Chief of the Legal Department of the NKID (Narodnii Komissariat Inostranih Del), or People's Commissariat for Foreign Affairs, the forerunner to the Ministry of Foreign Affairs.