Objective: To report two newborn cases, one with retinal vascular changes and both with sensorineural hearing loss, which development factor could be neonatal polycythemia. Case Description. Case 01. A full-term newborn, without signs of perinatal asphyxia, developed symptomatic polycythemia on the second day of life and was treated with parenteral hydration. After 02 days, it developed retinal occlusion of the left vein and failed hearing screening test, which persisted in subsequent evaluations. Case 02. A full-term newborn, without signs of perinatal asphyxia, developed symptomatic polycythemia on the second day of life, treated with parenteral hydration. Neonatal hearing screening was normal, however, when repeated after three months, it developed sensorineural hearing loss in the left ear. Comments: Neonatal polycythemia is characterized by elevated levels of hemoglobin (above 22g/dL) and hematocrit (above 65%). Most affected newborns are asymptomatic. Simptoms may be secondary to hyperviscosity, which reduces blood flow and impair tissue oxigenation. There could be an association between neonatal polycythemia and retinal vascular changes or hearing loss, in which the reduction of blood flow secondary to hyperviscosity can be critical tissue with high oxygen demand. Retinal vascular changes due to neonatal polycythemia are rare, and there are no case reports of hearing loss associated to this condition. The main causes associated with retinal occlusion of the retinal vein were not found in case 01. Furthermore, the main causes related to neonatal hearing loss, including congenital infections and significant neonatal jaundice, was not present in the two cases of sensorineural hearing loss.