Objective: To determine the biochemical and acute phase proteins changes in sheep experimentally infected with Anaplasma ovis (A. ovis). Methods: One Iranian sheep naturally infected with A. ovis (parasitemia 0.02%) but with no other blood parasites based on blood smear and polymerase chain reaction methods was selected as donor, and it was splenectomized to induce high level of parasitemia. Then, three weeks after splenectomy when parasitemia was 6%, donor’s blood was intravenously administered to each recipient animal. Five 5-6 months old Iranian male sheep without any blood parasites were selected as recipient animals. The percent of parasites, packed cell volume, serum biochemical parameters (urea, creatinine, bilirubin, aspartate aminotransferase activity, cholesterol, total protein, albumin, globulin, Fe), acute phase proteins (haptoglobin, total iron binding capacity, fibrinogen), were evaluated in sheep before and after being experimentally infected with A. ovis (until day 38). In addition, body weights of sheep were measured on days 0, 20 and 38. Results: In recipient sheep, microscopic examination of erythrocytes revealed a significant rise of parasitemia on days 12 and 15. The lowest level of packed cell volume in sheep was seen on day 15 post infection. A significant rise existed in mean urea and bilirubin (total, direct and indirect) on days 15 and 20. The increase of indirect bilirubin level was higher than direct bilirubin. Furthermore, serum Fe significantly increased on days 20 and 23. The mean total protein concentration significantly increased on day 38. A significant increase was found in the serum globulin concentration from days 20 and 27 to 38. Maximum values of haptoglobin were observed on days 27 and 30. Moreover, aspartate aminotransferase activity (from days 20-30) and cholesterol concentration (on day 20) significantly decreased. However, no significant changes were found in other parameters. Conclusions: Experimental ovine anaplasmosis caused by A. ovis could be associated with some changes in measured parameters, which presumably could be helpful for evaluation on staging of disease.