In a radio lecture delivered five years after the posthumous publication of the print score in 1953, Theodor W. Adorno described Anton Webern’s Piano Quintet as an “amalgamation of Brahmsian with Wagnerian elements,” which lends the work with a “double-character between formal coherence on the one hand and sparkling expressivity on the other.” In this paper I seek to argue that this “double-character” is best understood in terms of a very specific—indeed, “romantic” or “post-Beethovenian”—vision of the sonata form. This vision hinges on a complex dialectic between “formal” and “material” aspects. With its two-part S-space design, non-dominant use of pedal points and tendency to obscure structural cadences, on the one hand the movement features several “deformational” strategies which high-classical theories of sonata form do not sufficiently account for. Moreover, the movement is characterized by multiple energetic waves and ensuing dramatic gestures of collapse, the use of elaborate functional harmony and extended playing techniques, which reshape the sonata form as a nervous, anxious system. Through a detailed analysis of the work in the light of the most recent developments in Schenkerian analysis and the New Formenlehre, this paper interprets these features as ramifications of what I will term the quintet’s agitating impulse, a motivic idea set up right in the opening bars that, both on the local and large-scale levels, strives towards its harmonic resolution, yet only manages to resolve in the coda. Tracing some of the ramifications of this Beethovenian imperative of goal-oriented motivic-harmonic processes through the quintet, I will interpret its erratic and “deformational” physiognomy as a direct outgrowth of these (failed) attempts at a resolution. In this way, this paper reveals the movement as an original response to the history of the sonata form and a pertinent case in point to think through some of the issues in the theory and analysis of turn-of-the-century sonata practices.