Hyperglycaemia commonly occurs in children presenting at the emergency department. In the absence of diabetic symptoms, this stress-related hyperglycaemia is considered a benign condition. We present a malignant cause of hyperglycaemia in an 11-month-old girl with concomitant symptoms of a neuroendocrine malignancy. One month earlier, she had undergone an episode of stress-related hyperglycaemia concurrent with fever during an upper respiratory tract infection. Current glucose level was 234 mg/dL (13 mmol/L) and the glycosylated haemoglobin level was 44 mmol/mol (6.2%) without metabolic acidosis. We observed periods of hyperglycaemia, sweating, flushing, hypertension and tachypnoea. Urinalysis showed high amounts of catecholamine intermediates. Abdominal ultrasound revealed a mass originating in the right adrenal gland. Histology confirmed the diagnosis of neuroblastoma. Hyperglycaemia in this patient was the first presenting symptom of a metabolically active neuroblastoma.