This study included recording the natural heavy infection with immature macrocysts (Sarcocysts) of Sarcocytis spp. in sheep. The sheep is one years old which is slaughtered at butcher shop at Mosul city in May 2018. This is the first case recorded of natural infection with immature sarcocysts of Sarcocystis spp. in Mosul city. Many of small nodules were observed during slaughter, these nodules are seen within esophageal muscles in different sizes and shapes, they were distributed randomly throughout esophageal muscles. Most of the sarcosystis were small in size the mean of size between 20-28×28-42 µm they were histological examination showed that presence of only metrocytes. This confirmed the diagnosis that the sarcocysts were immature macrocysts (sarcocysts) for the Sarcosystis spp. In our study, heavy infected case with Sarcocystis reveals the fact that large numbers of cats(final hosts) in contact with sheep in pastures is considered the main risk factor for infection and feed with raw meat from infected sheep, which is very important for carcass condemnation when the meat inspection when abnormalities are found which indicate that the part of carcass, is unfit for human consumption it is condemned, which means the economic loss for livestock.