Troyanovsky was born into diplomatic family. His father, Aleksandr A. Troyanovsky, served as the first Soviet ambassador to the United States from 1934 to 1938. Although he was born in Moscow, Oleg attended the Sidwell Friends prep school in Washington, D.C., and Swarthmore College in Pennsylvania. At Swarthmore in the 1930s, Troyanovsky recruited his American classmate Stephen Laird as a Soviet spy.
Troyanovsky returned to the Soviet Union to complete his education at the Moscow Institute for Foreign Languages and Moscow University. After spending two years as a soldier in the Red Army, Troyanovsky joined the Russian Foreign Ministry to work as a foreign policy assistant and interpreter for Soviet leaders Josef Stalin and adviser to Nikita Khrushchev.
Troyanovsky served as the Soviet Union's ambassador to Japan before he was appointed to the United Nations. In 1980, two members of a dissident Marxist group sneaked into the U.N. Security Council chamber and threw red paint on Troyanovsky and U.S. Ambassador William vanden Heuvel. The Russian's response: "Better red than dead." In 1983 when listening to the recording of Soviet fighter pilots shooting down Korean Airlines Flight 007 jumbo jet near Moneron Island that killed carrying 269 people, Troyanovsky remained poker-faced and impassive.
From 1986 to 1990, he held his final diplomatic post as the ambassador to China. Troyanovsky spent his retirement years working on his memoirs and giving lectures in Russia and abroad.