In the present study, serum samples obtained from Holstein cattle, native cattle, sheep, goats, and camels in Al-Qassim, and surrounding regions were tested for bovine leukemia virus (BLV) antibodies for different animal species. Agar gel immunodiffusion was carried out using commercial diagnostic reagents. All samples of herds having positive cases with immunodiffusion were tested by ELISA. Positive cases were recorded among samples of the Holstein cattle with both serological tests. Prevalence rates differed from one farm to another and with both serological tests. With agar gel immunodiffusion, the prevalence rate in 3 farms were 43.13%, 21.79% and 6.25%. The prevalence rates with ELISA in the same herds were 52.94%, 34.01% and 6.25% respectively. Tested samples of two more herds showed no evidence of infection. Concerning native cattle and other animal species tested, no positive cases were recorded. The results indicated that bovine leukosis exists among dairy farms specially the farms owning Holstein animals that have been imported from the United States of America. The findings should be taken seriously, as the infection is infectious and one case on a farm can spread the infection easily to the rest of the animals. Therefore, farms should be tested for infection and positive animals are to be discarded under a national control program.