Holoprosencephaly is a developmental defect caused by incomplete cleavage of the embryonic forebrain structures during early embryogenesis. We describe a 3-month-old boy with median cleft palate, surgically reconstructed cleft lip, hypotelorism with a flat nose, cryptorchidism, clubfoot, and microcephaly. During the laboratory investigation, his blood sodium level was 154 mmol/L and urine specific gravity was 1.007. Serum osmolarity was 317 mOsm/kg and urine osmolarity was 268 mOsm/kg. Given these findings and the clinical response to vasopressin, diagnosis of central diabetes insipidus was made. Magnetic resonance imaging revealed semilobar holoprosencephaly. The patient responded very well to vasopressin treatment with restoration of serum electrolytes, which remained within normal limits on follow-up. In case of midline facial defects accompanied by hypotelorism with or without developmental delay, the brain should be imaged to confirm its morphology and investigations should be directed by a high index of suspicion of associated endocrinologic dysfunctions.