In this study the alterations in serum biochemical parameters of horse with leptospirosis was investigated. For this aim, 8 h with leptospirosis, were determined by the microscopic agglutination test and 8 healthy horses were used as material. The levels of serum glucose, urea, ceratinine, uric acid, total cholesterol, high-density lipoprotein (HDL), creatinine kinase (CK), sodium, potassium, chloride, calcium, phosphorus, magnesium were evaluated in leptospirosis cases and healty horses. Although we found significant decreases in levels of glucose (p < 0.01), uric acid (p < 0.01), HDL cholesterol (p < 0.05), ALP (p < 0.01), Cl (p < 0.01), Ca (p < 0.05), P (p < 0.001) in horses with leptospirosis, level of urea (p < 0.05) in horses with leptosprosis showed significant increases. The results obtained may suggest that these parameters might have taken part in the diagnosis and treatment of horse leptospirosis.