Troyat was born Levon Aslan Torossian (, Lev Aslanovich Tarasov) in Moscow to parents of Armenian descent. His family fled Russia in anticipation of revolution. After a long exodus taking them to the Caucasus on to Crimea and later by sea to Istanbul and then Venice, the family finally settled in Paris in 1920, where young Troyat was schooled and later earned a law degree. The stirring and tragic events of this flight across half Europe are vividly recounted by Troyat in Tant que la terre durera.
Troyat received his first literary award, Le prix du roman populaire, at the age of twenty-four, and by twenty-seven, he was awarded the Prix Goncourt.
Troyat published more than 100 books, novels and biographies, among them those of Anton Chekhov, Catherine the Great, Rasputin, Fyodor Dostoyevsky, Ivan the Terrible and Leo Tolstoy.
Troyat's best-known work is La neige en deuil, which was adapted as an English-language film in 1956 under the title The Mountain.
Elected as a member of the Académie française in 1959. At the time of his death, Troyat was the longest-serving member.