Although the book is mainly in Russian, significant portions of dialogue are in French. It has been suggested that the use of French is a deliberate literary device, to portray artifice while Russian emerges as a language of sincerity, honesty, and seriousness. It could, however, also simply represent another element of the realistic style in which the book is written, since French was the common language of the Russian aristocracy, and more generally the aristocracies of continental Europe, at the time. In fact, the Russian nobility often knew only enough Russian to command their servants; Tolstoy illustrates this by showing that Julie Karagina, a character in the novel, is so unfamiliar with her country's native language that she has to take Russian lessons.
The use of French diminishes as the book progresses. It is suggested that this is to demonstrate Russia freeing itself from foreign cultural domination, and to show that a once-friendly nation has turned into an enemy. By midway through the book, several of the Russian aristocracy are eager to find Russian tutors for themselves.