Third Movement: Adagio in B major, 4/4 time

The movement is in ABA' three-part form. The theme of the A section features a dialogue between the piano and string parts. The B section consists of a lively theme, a response based on a dotted rhythm motif, and thematic variations. The rhythm and leaping figures of the theme recall the post-cadential phrase of the A section's theme. In the A' section, the piano embellishes the post-cadential phrase, and the continuous piano timbre and voice leading enhance the overall unity of the A' section.

The tonal structure, a minor third relationship common with the first movement, B major (A section) → G-sharp (B section), is already anticipated in the theme of the A section (B major → G-sharp minor, measures 7-13). As seen in the transition to the B section and the beginning of the recapitulation, E major, which is the subdominant of B major and the relative major of G-sharp minor, serves as a key for modulation. However, Brahms seems to have regarded E major not merely as a transitional medium but as a significant key for the movement. The modulation to E major in the response of the B section's dotted rhythm motif would serve as evidence for this.