Parasite-induced changes in host dispersal behavior are now recognized as a key predictor of the spread and persistence of parasites in space. However, current theories treat post-infection dispersal strategies as a fixed trait, and the condition-dependent nature of host responses to parasite infection (i.e., plasticity) has long been underappreciated. Here, using a tractable host-parasite system, we provide the first evidence that parasite infection induces size-dependent host dispersal. A simulation model supports that the observed dispersal plasticity is critical for the persistence of parasites. These results suggest that host dispersal plasticity is an integral component to understand how parasites emerge, spread, and persist in nature. Our findings provide a novel starting point for building a predictive model for parasite/disease epidemics.