The article discusses the words ‘secret’, ‘mystery’ and ‘riddle’ functioning in Fyodor Dostoevsky’s creative works of different genres and periods of creativity, makes the assumption that these words have the status of idioglosses, i. e. they characterize specific features of the author’s idiostyle and worldview. Contains the reasoning about the genre features of Dostoevsky’s creative works and the results of linguistic and literary research related to the study of the words ‘secret’ and ‘mystery’ semantics. Analyzes the definition of the word ‘secret’ in various dictionaries including a fragment of the dictionary entry from the Dostoevsky’s Language Dictionary, gives a similar lexicographic description of the word ‘mystery’: subordinate, coordinative and associative links of the word are systematized, junctions of several textual associative fields are found out. The article contains comparative lexicographic analysis of the contexts of the words ‘secret’ and ‘mystery’ using in order to explicate the components of their meaning in Dostoevsky’s texts. As a result in the context of Dostoevsky’s idiostyle description the definition of the word ‘mystery’ is formulated and additional shades of the word ‘secret’ meaning are revealed. Thus, a significant fragment of the author’s thesaurus is reconstructed in the article.