Congenital methemoglobinemia is a rare cause of cyanosis in a newborn. Methemoglobin (MetHb) is a form of haemoglobin (Hb) in which heme iron is oxidized and unable to bind oxygen. The causes of methemoglobinemia are classified as congenital or acquired. We herein report a case of a preterm neonate with cardiopulmonary compromise and cyanosis, eventually diagnosed to have congenital methemoglobinemia. The baby developed cyanosis, which did not improve on oxygen supplementation. Blood gas analysis showed raised Methb levels which was further confirmed by co-oximetry. The baby was started on Oral Vitamin C and improved subsequently and was discharged in a stable condition.