We report on a newborn baby with partial trisomy 13 who presented with multiple dysmorphic features and hyperinsulinaemic hypoglycaemia. Cytogenetic study on peripheral blood lymphocytes showed 47,XY,+mar in all cells analysed; fluorescent in situ hybridisation showed that the marker was solely derived from chromosome 13. The final karyotype was 47,XY,+del(13)(q14q32). Milk formula through a nasogastric drip and intravenous glucose infusion were given to prevent further hypoglycaemia. However, the baby developed occasional episodes of hypoglycaemia during bolus feeding. Hence, diazoxide was given, at a dosage of 10 mg/kg per day from day 24. Thereafter, no hypoglycaemic episodes were detected. Subsequent follow-up revealed satisfactory growth, global developmental delay, and left divergent squint.