Corals (Cnidaria; Anthozoa) play critical roles as habitat-forming species with a wide range, from warm tropical to cold deep-sea environments. Here, we characterize the eukaryome of fireworms (Hermodice carunculata), a coral predator, and explore potential transmission routes of microeukaryotes between predator and coral prey. Our results reveal a diverse microeukaryotic community associated with fireworms, including several taxa also found in corals, suggesting potential bidirectional transmission of microeukaryotes between these organisms.