Equine theileriosis, an OIE listed disease caused by Theileria equi is an economically important haemoprotozoan disease of horses in tropical and subtropical parts of the world. The aim of the present study was to monitor the biochemical alterations in order to find out the severity of the disease. Standard assay kits were used to study the biochemical parameters of horses positive for theileriosis in comparison with healthy ones. Out of 75 serum samples, 25 samples were collected from horses positive for theileriosis and 50 from healthy horses. The serum levels of GPT (32.00±2.30 U/L), GOT (350.84±27.87 U/L), GGT (20.95±0.92 U/L), LDH (823.74±102.93 U/L), total protein (8.11±0.37 g/dl), globulin (3.84±0.40 g/dl), BUN (46.26±5.27 mg/dl) and creatinine (1.33±0.18 mg/dl) were found to be significantly increased (p less than 0.01) in infected horses compared to the healthy group. Non- significant elevation (p greater than 0.05) in total bilirubin (1.08±0.14 mg/dl), unconjugated bilirubin (0.57±0.11 mg/dl) and glucose (102.57±30.41 mg/dl) as well as non-significant reduction (p>0.05) in conjugated bilirubin (0.42±0.04 mg/dl), albumin (4.26±0.24 g/ dl) and A/G ratio (1.55±0.30) were also observed in infected group. There was no significant alteration (p>0.05) in the level of serum calcium (12.32±0.36 mg/dl) and phosphorus (4.53±0.33 mg/dl), as compared to the healthy group. Significant elevation of GOT, GPT, GGT, BUN and creatinine revealed the involvement of liver and kidney functions in T. equi infected horses.