BACKGROUND: Sarcocystis infection is one of the most common zoonotic protozoon diseases caused by different Sarcocystis spp. Objectives: Due to the importance of this infection in public health, the infection rate of macroscopic and microscopic cysts in sheep and cattle of abattoir of Shahriar, was investigated. Methods: 138 slaughtered sheep and cattle were selected randomly and their esophagus, diaphragm, heart, tongue, masseter and intercostal muscles were separated. In order to find cysts, the samples were examined by two methods: direct observation for macroscopic cysts and finding microscopics cysts by smear dab, Giemsa staining and microscopic investigation for bradyzoites of parasite. Results: In slaughtered samples, there was no macroscopic cyst but microscopic cysts were positive in 93.48% of cattle and 86.95% of sheep by impression smear method. The results showed the significant difference between different muscles and microscopic cysts (p<0.05) .Heart and esophagus were the most infected and tongue was the least infected part. Infections in males were more than females in both sheep and cattle. There was no significant different in various ages of cattle, however, infection in sheep less than one year old, were higher than the other ages. ConclusionS: Due to the heavy Sarcocystis infection in meat of cattle and sheep and the importance of this parasite in public health, it is suggested to avoid eating raw and undercooked meat and conduct preventive measures such as closer inspection of carcasses and local or total removal of slaughtered in abattoir.