We describe a 4 year old girl with acute Aeromonas hydrophila gastro-enteritis who presented with a combination of hypercalcemia, metabolic alkalosis, and renal impairment. Serum parathyroid hormone was not elevated. Both milk-alkali syndrome and intoxication of vitamins A and D were ruled out. The hypercalcemia, metabolic alkalosis, and renal impairment were improved by fluid infusion and intravenous administration of furosemide. Gastro-enteritis also improved with oral administration of the antibiotic norfloxacin. The association of A. hydrophila gastro-enteritis with hypercalcemia has not been described previously.