This article examines the characteristic features of the cello and piano sonata shaped by the aesthetic principles of Impressionism. The study focuses on the interaction between the cello and piano as equal partners, emphasizing timbral color, fluid texture, and expressive nuance. Special attention is given to modal harmony, extended tonality, flexible rhythm, and subtle dynamic shading as defining elements of the Impressionist style. Through analytical observation of form, melodic development, and performance techniques, the article reveals how Impressionist thinking transforms the traditional sonata genre into a refined soundscape driven by atmosphere and emotional suggestion rather than dramatic contrast.