Hemogram, acid base balance, blood gas analysis and acute phase response have been evaluated in horses clinically infected with babesiosis in Mosul, Iraq. The study was conducted on 100 local horse breed ranging from 3-10 years old of both sexes. Eighty local horse breed were clinically infected with Babesia spp < /em>.which diagnosed by Giemsa stained blood smears and confirmed by C-Elisa test. 20 clinically normal horses served as control group. Results indicated statistically significant decrease (P<0.05) in TRBCs, Hb, and PCV values in diseased animals, Macrocytic hypochromic type of anemia was found and the percentage of hemoparasitism (parasitemia) ranged between (5-24%)with a mean of (16.57%).The results also indicated a significant increase in TLC as a result of significant increase of lymphocytes. Babesia equi were detected in 63.75% whereas Babesia caballi detected in 36.25%. Statistically significant decrease were encountered in blood pH, Pco2, bicarbonate ions, Base excess and Oxygen saturation percent (So2) in diseased horses than in controls, However statistically increase in anionic gab have been detected, Moreover titrational metabolic acidosis were indicated. Statistically significant difference have been encountered in acute phase response as haptoglobin and fibrinogen values were decreased in clinically infected horses. It have been concluded that different adverse effect, hemolytic anemia, tissue hypoxia beside decrease acute phase response were encountered in horses infected with Babesia spp.