Mastitis, inflammation of the mammary gland, is one of the most common reasons for culling ewes in commercial sheep flocks. Mastitis is usually due to a bacterial infection. To investigate the periodic prevalence, etiology and some epidemiological features of subclinical mastitis in ewes from the Sarab region, milk samples from 160 lactating ewes were aseptically collected for bacterial examination. An association was observed between the occurrence of subclinical mastitis and the age of ewe. The periodic prevalence rate of SCM was 7.5%. Staphylococci were the most prevalent bacteria, representing 83% of the isolates. Coagulase-negative staphylococci (CNS) (71%), was the most prevalent species followed by Staphylococcus aureus (12%), Escherichia coli (9%) and Corynebacterium (8%) of the isolates. In conclusion, subclinical mastitis seemed to be an important health for milking sheep in the Sarab region of Iran.