DEND syndrome is a very rare syndrome of permanent neonatal diabetes mellitus, with an incidence of < 1/1000,000. It is defined as a triad of developmental delay, epilepsy, and neonatal diabetes. We report the case of a 9-month infant girl who presented with the most severe form of neonatal diabetes mellitus spectrum along with developmental delay and epilepsy. Genetic mutation testing confirmed mutations in KCNJ11 gene encoding the Kir6.2 subunit of the K-ATPchannel, which are involved in insulin secretion. The use of oral sulfonylureas in treatment of such patients is showing promising results worldwide. The authors strongly recommend early referral and checking for genetic mutations in all patients of neonatal diabetes mellitus.