CD200 is a cell surface glycoprotein that binds an inhibitory receptor (CD200R) on myeloid cells. CD200 orthologues are present in many species of virus, and we show that the rat cytomegalovirus CD200 orthologue (e127) is expressed at the cell surface on infected cells. It binds the host CD200R with the same affinity as that of the host protein, and thus this protein acts as a close mimic of the host protein and has the potential to downregulate immune responses to the virus.