This study aimed to determine the etiology of haemoglobinuria occurring in pregnant buffaloes (mid to advanced). For this purpose, blood samples from four haemoglobinuric and four apparently healthy pregnant buffaloes (mid to advanced) were collected and analyzed for haemato-biochemical constituents. The feeding history and feed intake were recorded for individual animal and feed samples were also collected and analyzed for calcium and phosphorus contents, from field cases occurred in Borkhedi village of Mhow Tahsil, MP (India). The most prominent clinical sign was passing of red to coffee colored urine depending upon severity and duration of illness. Milk production in affected buffaloes had completely ceased. The faeces were normal to hard or sometimes loose in consistency. The occurrence of haemoglobinuria was observed in the summer season. All the affected buffaloes were in there 3rd-4th lactation. The calcium intake by haemoglobinuric buffaloes (128.87+2.59 g/day) was greater as compared to healthy buffaloes (54.25+2.96 g/day), whereas phosphorus intakes by haemoglobinuric buffaloes (16.35+0.84 g/day) and by healthy buffaloes (17.25+0.69 g/day) were similar. The calcium and phosphorus intakes ratio in haemoglobinuric buffaloes (7.9:1+0.39) was higher as compared to healthy buffaloes (3.2:1+0.22). In the haemoglobinuric buffaloes, mean haemoglobin (Hb) concentration, packed cell volume (PCV) and plasma inorganic phosphorus were significantly (at P LT 0.05, P LT 0.01 and P LT 0.01, respectively) lower, while blood glucose and creatinine levels were significantly (P LT 0.05 and P LT 0.01) higher as compared to those values in healthy buffaloes. It was concluded that haemoglobinuric buffaloes were suffering from hypophosphatemia, leading to haemoglobinuria and anaemia