In order to identify and differentiate Theileria orientalis in cattle which may be infected with Theileria annulata simultaneously, a semi-nested PCR was performed. Thus, 160 blood samples were collected from apparently healthy native cattle in Golestan province of northern Iran, during 2009 to 2011. The Tbs-S/Tbs-A primer set derived from the 18S rRNA encoding gene was used for first PCR amplification, and the amplified sequence weight by this primer set for Theileria sp. was 426-430 bp. Then, DNA solution from purified PCR product was used for the semi-nested PCR analysis. The first PCR product amplified using T. orientalis primer set (To-S/Tbs-A) derived from the 18SrRNA encoding gene, and this specific primer weight was 235 bp. Also, the first PCR product amplified using T. annulata primer set (Ta-S/Tbs-A) derived from the 18SrRNA encoding gene and this specific primer weight was 193 bp. Having extracted DNA of each sample, using Tbs-S/Tbs-A primer set for PCR and analyzing the PCR products on the 2% agarose gel electrophoresis, 13 out of 160 blood samples (8.12%) were positive for Theileria sp. Meanwhile, performing semi-nested PCR with T. orientalis-specific primers, 9 out of 13 blood samples (5.62%) were positive and performing semi-nested PCR with T. annulata-specific primers, 12 out of 13 blood samples (7.5%) were also positive. This molecular assay approves the presence of T. orientalis in the native cattle of northern parts of Iran for the first time. In addition, this procedure will detect the concurrent infection of T. orientalis and T. annulata in the cattle too.