A 40-year-old woman presented with a 10 day history of episodic vagueness, speech disturbance and blurred vision. Episodes typically occurred in the morning after awaking from sleep and resolved with food ingestion. She had no past medical history, did not drink alcohol and was not on any medication. Physical examination was normal with no evidence of endocrinopathy. After 10 h of fasting, she became hypoglycaemic with evidence of neuroglycopenia, which resolved with intravenous dextrose. Biochemical investigations revealed decreased glucose, insulin and C-peptide values with an increased excess insulin-like growth factor II: excess insulin-like growth factor I (IGF-II: IGF-I) ratio. Radiological examinations of the abdomen and pelvis revealed a heterogenous 10.5 cm left renal mass. The patient underwent a radical left nephrectomy. She had complete resolution of hypoglycaemic events. Histology revealed a renal sarcoma, grade 2/3. This is the first report in the literature involving a renal sarcoma causing non-islet cell tumour hypoglycaemia via excess IGF-II secretion.