Thirty-five multiparous anestrous cows were infested with Trematode parasites used to determine the effect of anthelmintic treatment on the reproductive performance and some blood constituents. The reproductive status of all animals and the changes in the ovarian activities were assessed by rectal examination. Faecal samples were collected from all animals directly after rectal examination. All animals were observed for estrus signs and those came in estrous were mated. Serum progesterone concentration was measured to determine ovarian activity prior to treatment and to confirm the occurrence of ovulation as well as to determine early pregnancies which were confirmed by rectal examination at 45 days post service. Serum samples were collected for determination of total proteins, calcium, inorganic phosphorous, estradiol and insulin like growth factor-I (IGF-I). The results of the present study indicated that, the most common parasitic infection in case of anestrum were fasciolia and paramphistoma. Anthelminitic treatment significantly (P < 0.001) increase the serum levels of calcium, inorganic phosphorus, estradiol, progesterone and IGFI. Anthelmintic treatment improves the reproductive performance of anestrous cows infested with Trematode parasites as indicated by higher oestrous response, higher (73.5%) first service and overall (83.33%) conception rates.