Renal excretion and cellular uptake of potassium play key roles in the body's defense mechanism against hyperkalemia. Intra-operative hyperkalemia is an uncommon life-threatening complication during elective renal transplant surgery. We report herewith a non-insulin dependent diabetic kidney transplant recipient with prolonged pre-operative fasting, in whom, despite pre-operative hemodialysis, unforeseen high serum potassium level suddenly presented as wide-complex bradycardia during the surgery. The patient responded well to medical therapy of the hyperkalemia and the surgery was completed uneventfully. It is difficult to single out the exact cause of hyperkalemia in our patient. Prolonged pre-operative fasting for about nine hours, associated with insulinopenia and hyperglycemia, in the presence of beta-blockade and metabolic acidosis, have probably collectively resulted in efflux of potassium from intra-cellular stores. This potentially catastrophic complication should be remembered in diabetic patients undergoing any type of surgery.