This article juxtaposes Marx’s critique of capitalism with recent developments in affect theory. My central argument is that a critique of the tension of capitalist affect is fundamental to a Marxian account of capital: on the one hand, capitalism amplifies the potential affective capacity of bodies through its development and organization of productive forces; on the other, it captures this increase to enrich the bourgeoisie, immiserate the proletariat, and reproduce capitalism. I also sketch the ways that an affective interpretation can provide insight into anti-capitalism resistance and post-capitalist life within Marx’s theoretical and philosophical project. Ultimately, reading Marx’s critique of capitalism for its resonances with Deleuzean-Spinozan affect theory not only generates a newfound apprehension of the affective register of that critique, but also adds to the critical repertoire of affect theory.