“Our brain is plastic and we do not know it” says French philosopher Catherine Malabou. This article argues that Joseph Conrad knew it. In the process it suggests that contemporary discoveries in the neurosciences about the “neuroplasticity” of the human brain can be supplemented by tracing the aesthetic and conceptual implications of the plastic transformations depicted in Conrad’s early modernist fictions. Conrad’s neuroplasticity has both a critical and a theoretical side. On the one hand reading Conrad’s Under Western Eyes and A Personal Record from the angle of what Malabou calls the “formative” qualities of plasticity casts new critical light on Conrad’s account of character formation literary impressionism and linguistic assimilation which in form his modernist practice. On the other hand Conrad’s modernist approach to the psycho somatic formation of fictional and real characters reframes Malabou’s concept of “plasticity” in light of a philosophical tradition that—via Philippe Lacoue Labarthe and Jacques Derrida—goes back to Rousseau and Plato. Such a genealogical reframing makes us see that the conceptual origins of plasticity can be traced back to the pharmacological qualities of mimesis and that aesthetics is central to the formation of this scientific concept. My contention is that Conrad’s neuroplasticity provides an important literary case study to work through the relation between mimesis and plasticity thereby contributing to the ongoing dialogue between literature and science.