Introduction Sirenomelia, also known as mermaid syndrome, is a very rare fatal congenital abnormality in which the legs are fused together, giving them the appearance of a mermaid's tail. It is commonly associated with abnormal kidney development, genital and rectal abnormalities. Only a handful of cases have been reported in other parts of the world and is very rare in India too. This case was diagnosed postnatal in a tertiary hospital in Nagpur city of central India. Case Presentation A preterm male baby of weight 1.1 kg was delivered by lower-segment caesarean section to a primigravida of age 26 years. Baby presented with fusion of the entire lower limbs, imperforate anus, indiscernible genital structures, single umbilical artery and a neural tube defect. He cried spontaneously with APGAR scores 5 at 0 and 8 at 5 min and expired after 4 h. His mother had a family history of diabetes in her paternal side. The postmortem chromosomal studies depicted 47XXY, i.e., Klinefelter's syndrome.