Hypoparathyroidism is one of the recognized causes of late-onset neonatal hypocalcemia. Maternal hypercalcemic hyperparathyroidism has been shown to suppress fetal parathyroid glands, causing transient neonatal hypoparathyroidism. We report two siblings (6 years apart) with transient hypoparathyroidism presented with hypocalcemic seizures during the first 2 weeks of life. Subsequent investigation revealed an unrecognized normocalcemic hyperparathyroidism with nephrocalcinosis in the mother. Maternal hyperparathyroidism was caused by two parathyroid adenomas. In conclusion, our report highlights the importance of careful evaluation of neonatal hypoparathyroidism in uncovering an unrecognized, asymptomatic hyperparathyroidism in the mother.