Wild Chinese Water Deer exist in large numbers in Northeast Asia, including South Korea. The deer population is so widespread that they are common even in urban areas, resulting in increased contact with humans and domestic animals. The purpose of this study was to examine the prevalence of Theileria sp. infection in wild Chinese Water Deer in South Korea. Using biomolecular techniques, blood samples taken from 18 wild Chinese Water Deer were examined. Thirteen of the 18 samples (72%) tested positive for infection. In 11 of the deer, a Theileria sp. was detected that is nearly identical to the highly pathogenic Theileria sp. reported in China. Theileria ovis and Theileria capreoli were also detected individually in two deer. These results indicate that there may be a high prevalence of Theileria sp. infection in wild Chinese Water Deer, and that the deer may act as a reservoir for the Theileria sp. infection of domestic animals.