The study was conducted to study the effect of Ultra-violet radiated Eimeria oocysts on immune pattern of lambs. For this purpose, Eimeria sp. (E. crandalis, E. granulosa, E. ovinoidalis, E. parva, E. pallida and E. faurei) were collected from infected sheep and propagated in a lamb for increasing the number of oocysts. The collected Eimeria sp. from the lamb, were sporulated in potassium dichromate 2.5% and divided into 3 parts; the 1st part was exposed to UV radiation for half hour and the 2nd part for one hour and the third left without irradiation. Nine lambs were classified into 3 equal groups; G1 was inoculated by half hour UV irradiated Eimeria oocysts, G2 was inoculated by one hour UV irradiated Eimeria oocysts and G3 was inoculated by non irradiated Eimeria oocysts. Fecal samples were collected from all lamb groups from 5th to 21th days, identified and count. Challenge by non attenuated Eimeria was carried out at 21th day post inoculation. The obtained results revealed that immunization of lambs by using one hour UV irradiated Eimeria oocysts showed low number of oocysts in feces before and after challenge compared to other groups. The same group also showed high level of γ globulin as well as increasing levels of IgG. It was recommended that immunization of lambs by one hour UV irradiated Eimeria oocysts could protect lambs against Coccidiosis. Keyword. Eimeria species, Lambs, UV irradiation, immunoglobulin, immunization.