Ocean acidification (OA) research has matured into a sophisticated experimental and theoretical scientific discipline, which now utilizes multiple stressor, mesocosm experiments, and mathematical simulation models to predict the near-future effects of continued acidification on marine ecosystems. These advanced methodological approaches to OA research also include the study of inter-specific interactions that could be disrupted if participant species exhibit differential tolerances to stressors associated with OA. The host-parasite relationship is one of the most fundamental ecological interactions, alongside competition and predation, which can regulate individuals, populations, and communities. The recent integration of competition and predation into OA research has provided great insight into the potential effects of differential tolerances to acidified seawater, and there is no reason to believe that expanding OA research to include parasitology will be less fruitful. This essay outlines our current, limited understanding of how OA will affect parasitism as an ecological process, describes potential pitfalls for researchers who ignore parasites and the effects of infection, and suggests ways of developing parasitology as a sub-field of OA research.