A total number of 26 cows were subjected to study. Out of them 16 cows were presented to the Veterinary Teaching Hospital, Assiut University, showed high fever 40-41.5▫C, enlargement of superficial lymph nodes, and infestation with ticks. Some cases accompanied with corneal opacity and lacrimation and represent the theileria infected group. The remained animals represented the control group. Blood samples were collected from animal under investigation and used for blood film, hematological and serum biochemical analysis. There were significant decreases in total RBCS counts (p<0.01), haemoglobin (Hb) concentration (p<0.01), packed cell volume (PCV) (p<0.01), platelets (PLT) count (p<0.01), plateletcrit (PCT) (p<0.01) in theileria infected group when compared with the control group. Serum biochemical analysis revealed significant decreases in serum total proteins (p<0.01), albumin (p<0.01), calcium (p<0.01), phosphorus (p<0.01) levels and LDH (p<0.01) activity. In addition, there were significant increases in serum BUN (p<0.05) and creatinine (p<0.05) levels, and in serum AST (p<0.01) and GGT (p<0.01) activities. Correlations between serum biochemical parameters revealed significant positive correlations between total protein and albumin (r= 0.598*), A/G ratio and albumin (r=0.860**), calcium and albumin (r=0.729*), calcium and A/G ratio (r=0.752*), GGT and BUN (r=0.539), and significant negative correlations between A/G ratio and globulins (r=0.809**) and between glucose and albumin (r=0.614). It could be concluded that theierlia infection in cattle resulted in anaemia, thrombocytopenia, hypoalbuminaeia, hypoproteinaemia and hypophosphataemia. It is recommended to supply cows suffered from theileriosis with supportive treatment to help the animal resume normal productivity early.