BACKGROUND: Schistosomiasis is considered as one of the most important infections in ruminants. The flukes are found in the blood vessels of animals. This parasite has been observed in many countries such as: Turkmenistan, Kazakhstan, Iran, Iraq and parts of Europe. OBJECTIVES: Aim of this study was to determine the contamination of Schistosoma turkestanicum in sheep in the central region of Mazandaran province during the year 2012-13. METHODS: Based on the high mortality rate reported by Mazandaran Veterinary Organization in some herds in the cities of the north of Iran During investigation 21.2% mortality was seen in infected herds by necropsy; Schistosoma turkestanicum was diagnosed  as cause of death. Examined infected herds and fecal samples were collected directly from the rectum of sheep.  Samples were examined by flotation method and obtained results were analyzed by statistical tests. RESULTS: During present study which was performed in five central cities of Mazandaran, the highest infection rate was found in Babolsar and the lowest was found in Moghrikola region of Babol. Mortality rate was also evaluated based on gender and it was shown that mortality rates in females were higher than in males (p<0.05). CONCLUSIONS: Ornithobilharziosis, is considered one of the endemic diseases in some parts of Iran and several epidemics have occurred in recent years in Iran. Because this parasite causes  significant economic losses in herds of sheep and goat in Iran, due to its location in the ruminants body and because Mazandaran province is one of the important foci of infection, more attention of the veterinary organization and its institutions is needed for better and greater control of infection.