Hepatozoon (Apicomplexa: Adeleina) is a genus of apicomplexan hemogregarine coccidia that infects amphibians, snakes, lizards, crocodilians, birds, and mammals; however, the occurrence of clinical disease varies across species. In squamates, severe infections can be associated with anemia and dehemoglobinization, but there are often no signs of illness or substantial lesions. Individual reports of disease associated with hemogregarine infection in snakes do occur, and therefore, there is a need to continue to investigate these poorly understood parasites. This report describes a case of hepatozoonosis in a captive Mexican black king snake (Lampropeltis getula nigrita). The snake exhibited approximately five days of lethargy before being found deceased. Relevant findings on post-mortem examination were pale lungs, a pale heart, and a small liver surrounded by pink-tinged coelomic effusion. Histologically, necrosis and inflammation in the liver and pulmonary serosa were associated with protozoa morphologically consistent with hemogregarines. 18S PCR and sequencing on formalin-fixed paraffin-embedded liver identified a Hepatozoon species with 100% homology to a parasite previously detected in Patagonia green racers (Philodryas patagoniensis). How the king snake contracted this parasite is unknown.