This study was performed to determine the prevalence of Theileria sergenti (T. sergenti) in cattle reared in eastern areas of Gyeongbuk province by PCR. Among 443 samples collected from 42 cattle farms, 96 (21.7%) samples from 13 (31.0%) farms were positive for T. sergenti. By regions, 87 (26.6%) out of 327 cattle in Gyeongju, 8 (9.5%) out of 84 cattle in Pohang, and 1 (3.1%) out of 32 cattle in Ulleung were positive for T. sergenti. T. sergenti infection in dairy cattle (27.9%) was significantly higher than that in Korean cattle (9.4%, P<0.0001). Accordingly, Korean cattle were more resistant to T. sergenti infection. Prevalence of T. sergenti in cattle was increased with age (P<0.0001). The infection rate in cows (23.3%) was significantly higher than that in bulls (5.0%, P<0.01). Seasonally, prevalence of T. sergenti in cattle was highest in autumn (32.7%, P<0.01). Prevalence of T. sergenti in grazing cattle (66.7%) was significantly higher than that in non-grazing cattle (15.8%, P<0.0001). Since prevalence of T. sergenti infection is high in cattle reared in eastern areas of Gyeongbuk province, survey on other hemoparasites and appropriate control programs need to be established in this region.