Both insufficient and excessive maternal iodine consumption can result in congenital hypothyroidism. In East Asian cultures, seaweed is traditionally consumed in high quantities by peripartum women as it is thought to improve lactation. We present a case of transient congenital hypothyroidism due to maternal seaweed consumption at a daily basis during pregnancy and lactation in a Dutch family without Asian background. This case highlights that even in families of non-Asian background, high maternal intake of iodine-rich seaweed occurs and can result in transient or permanent hyperthyrotropinemia in the neonate with risk of impaired neurodevelopmental outcome if untreated.