Stem cells are the base for cell therapy due to their ability to self-renew, differentiate into other cell types, and live throughout the life of an organism. The initial cell therapy was bone marrow transplantation; bone marrow that contains haematopoietic stem cells is transferred from a healthy donor into a sick recipient to transfer the healthy genotype 1,2 . Stem cell therapy approach may be possible in corals, where there is genotypic variation in heat tolerance that influences survival during increased water temperatures 3–5 . However, we first need the ability to reliably isolate and transplant stem cells in Hexacorallia, which includes stony corals and sea anemones 6 . In this work, we used the sea anemone Nematostella vectensis as our model for candidate stem cell transplantation, as it is the only hexacorallian species that has fluorescent-tagged transgenic strains 7 . We established cell transplantation to show that there are cell populations exhibiting the functional characteristics of stem cells. We showed that a subpopulation of cells from N. vectensis can be transplanted from donor to recipient, are long-lived and self-renewing, can proliferate and differentiate, can integrate into the recipient, and rescue recipient animals treated with lethal doses of a chemotherapeutic agent. Lastly, we showed that this subpopulation can be enriched by sorting, using species non-specific cell markers and that similar subpopulations of cells can be isolated from other hexacorallians, including stony corals. This lays a foundation for the possibility of stem cell-based therapy in species of Hexacorallia.