The paper deals with studying language deviations of different types in James Joyce’s Ulysses and Finnegans Wake. Deviations in general are known to be a departure from a norm or accepted standard; in linguistics deviations are viewed as an artistic device that can be applied in different forms and at various textual levels. The author’s language deformation is analyzed as a form of deviation used for expressing the writer’s language knowledge. It is concluded that in Ulysses the destruction of the language is thoroughly thought out and multi-aimed. For instance, occasional compound units that dominate the novel imitate the style of Homer, reviving the ancient manner in contemporary language. Despite the use of conventional word-building patterns, rich semantic abundance being the basic principle of Joyce's poetics seriously complicates interpretation of the new words in the source language. The attempt is also made to systematize deviation techniques in Finnegans Wake. In particular, multilinguality is found to be the base of the lexical units created by J. Joyce. Such hybrid nonce words produce the polyphony effect and trigger the mechanism of polysemantism together with unlimited associativity of the textual material, broadening the boundaries of linguistic knowledge as a whole. Additionally, certain results of a deeper comparative analysis of the ways to translate the author’s deviations into Russian are given. The analysis of three Russian versions of Ulysses and the experimental fragmentary translation of Finnegans Wake show that there exists some regularity in the choice of translation method, particularly its dependence on the structural similarities/ differences of the source and the target languages, as well as the language levels affected by J. Joyce in the process of lingual destruction. The impossibility of complete conveyance of the semantic depth of the text and stylistic features in the target language is noted.