The magnesium deficiency may affect buffalo calves with no clinical presentation and is also associated with reduced production and increased susceptibility to disease. The current study was conducted to diagnose subclinical hypomagnesemia in buffalo calves. The work conducted north of Basrah took 25 normal and 75 diseased calves, then drew whole blood and serum samples for complete blood count and biochemistry assay. Results show that magnesium concentration shows the level in mmol/L as 0.56±0.01 and 1.03±0.03 for deficient and healthy calves, respectively. Deficiency signs were pale mucous membrane, loss of appetite, stunted growth, anxiety, emaciation, tremor, and grinding teeth, an increase in respiratory and cardiac rates, and a reduction in ruminal contraction. The blood examination revealed a significant decrease in levels of erythrocytes, hemoglobin, and packed cell volume, as well as an increase in mean corpuscular volume and concentration of mean corpuscular hemoglobin, resulting in macrocytic hyperchromic anemia. Additionally, there was an increase in relative neutrophil and monocyte, and a decrease in lymphocyte and eosinophil, but no variation in total leukocyte count. The biochemical analysis included significant decreases in levels of albumin, alkaline phosphatase, calcium, phosphorus, sodium, and total protein, and a significant increase in potassium with respect to control buffalo calves.