Guillain-Barré syndrome (GBS) is an acute inflammatory polyradiculoneuropathy that can cause total motor paralysis in severe cases. Reports of hypercalcaemia in patients with GBS are rare. Plasmapheresis, an extracorporeal blood purification procedure for the removal of large molecular weight substances, is a wellestablished therapy for ventilated GBS patients. Although it has been observed in a few reported cases, theoretically, hypercalcaemia is not described as a plasmapheresis-related problem unless there is an underlying cause. We present a rare case of an 8-year-old child presenting with headache, diplopia, and squint, followed by disturbed conscious levels and paralysis. He was treated with both intravenous immunoglobulin and plasmapheresis, with a favourable outcome. We made a laboratory observation of hypercalcaemia which was associated with the plasmapheresis therapy without any related underlying cause. This raises the need for similar observations and the gathering of other possible acceptable explanations.