Abstract: This article is dedicated to the Third Sonata for Violin and Piano by José Antônio de Almeida Prado – one of the brightest chamber works of his later years. As of today, the specificity, characteristic traits and logical origins of Prado’s works have only partially been interpreted and explained in separate articles of Brazilian musicologists. The author’s goal was to study the specificity of the stylistics of this sonata, particularly to analysis it's musical language and structure, including the specific complex of the tonal and modal harmonic means, mixed chords of a complicated structure, as well as the forms and methods of thematic development. The author utilized traditional musicological procedures, used in the field of modern harmony and analysis. Based on this analysis, the author makes the conclusions that the principles of the thematic development in this sonata are used as classical – various types of imitations, rearrangement of voices, variations of separate elements of the sound material, as well as specific – dictated by the individual peculiarities of the material. In the pitch organization of the sonata the special role is played by the modal expressive means; overall however, the sound texture of the sonata leans on the twelve-tone system, forming as the result of the overlaying of the diatonic scales, tonal alteration, and usage of polychords. Such analysis is conducted for the first time.