The apicomplexan protozoans of the genera Hepatozoon, Babesia, and Cytauxzoon are emerging parasite pathogens that are increasingly diagnosed in the pet population. These tick-transmitted apicomplexan parasites are becoming more widely recognized as serious canine or feline pathogens. This article reviews the epidemiology, diagnosis, treatment, and control of canine hepatozoonosis and babesiosis, and feline cytauxzoonosis.