Equine theileriosis is considered as a serious problem because of harmful effects on the health and performance of equids. Despite the importance of this disease, there are few studies in related to clinical pathologic changes in equine theileriosis especially in horses. In this study, the oxidative stress biomarkers, cytokines, enzymes, lipid profile, electrolytes, minerals and some metabolites were evaluated in horses naturally infected with Theileria equi (n=22) and healthy (n=7). In infected horses, the serum concentrations of MDA, IFN-gamma, total protein, globulin, bilirubin (total, direct, indirect), triglyceride, glucose, iron, chloride, sodium and copper with enzyme activities of ALP, AST and GGT were found significantly higher, however concentrations of GSH, albumin, total cholesterol, HDL, TIBC, calcium, phosphorus, magnesium, potassium, zinc and manganese with enzyme activity of CAT were found lower when compared to the healthy horses (P<0.05). The changes in TNF-alpha, creatinine, urea and LDL concentrations were not statistically significant (P>0.05).The results indicate that there are significant changes in the oxidative indicator, cytokine, and biochemical parameters of horses in T. equi infection and that these changes may be useful in the evaluation of the diagnosis, prognosis and treatment of theileriosis. In addition, comprehensive studies are needed to better understand the role of cytokines in the pathogenesis of theileriosis.