The third movement, titled "Passacaglia", is solemn yet simple, and the most introspective movement throughout the entire Piano Trio. Written in just 88 measures, it possesses a structure akin to a single brushstroke, beginning at pp, reaching ff in the middle section, then diminishing towards the end, concluding at pp.

In Ravel's own lecture held at the École Normale de Musique in June 1925, he stated, "By emphasizing the slowness of the piece, a funereal atmosphere is created."

While Le Tombeau de Couperin (composed 1914–17), written in mourning for friends who died in the war, inherits the form of the old French suite, this movement also employs the passacaglia, a dance once popular in France, as if subtly alluding to the future of France facing war.