The article verifies the hypothesis that Leo Tolstoy’s diary has the form of a hidden dialogue of the writer with various subjects: with himself, with third parties, with God. Dialogue is understood as a form of individual development. The article determines that Leo Tolstoy’s diary represents a program of self-improvement, which is achieved through goal-setting and self-assessment. In the traditional perception of the diary genre, entries are interpreted as a form of autocommunication, carried out for the purpose of self-identification of the individual. The paper reveals that the form of the dialogue with oneself in some cases reaches the phase of the nominative multiple personality disorder. The writer defines himself as a third person: Tolstoy, Lev Nikolaevich, etc. The dialogue with oneself consists in evaluating one’s own actions, dispraising, moralizing, and goal-setting, and is one of the forms of self-development. The article establishes that Tolstoy looks upon the diary as a form of communication with third parties – readers of his notes. Diary entries of this type are aimed at modeling the diary readers’ behavior. One more type of communication is a dialogue with God. Tolstoy writes down many prayers, appeals to God, thinks about God, reflects with Him. He moves away from the idiomatic text of the prayer. Communication with God becomes intimate, containing a request for help in moral self-improvement. The semantic dominant of prayer is the good, benefit for others. Tolstoy excludes from prayers specific requests for material goods, i.e. common requests which people turn to God with. Leo Tolstoy’s diary is a heterogeneous genre formation, that is determined by the goals of the entries. The writer extends the functions of the diary. This feature determines the choice of communication tactics, the style of the diary. Tolstoy’s diary is a multi-genre formation that includes such sub-genres as a chronicle, explanation, a prayer, reasoning, reproach, accusation, etc.