Supported by the Secretary of Health Surveillance, Ministry of Health of Brazil, and by grants from the Wellcome Trust (213589/Z/18/Z, to Dr. Paixao), the Wellcome Trust with the U.K. Department for International Development (205377/Z/16/Z, to Dr. Barreto), the British Council Newton Fund (527418645, to Dr. Brickley), and the European Union Horizon 2020 Research and Innovation Program under the Zika Preparedness Latin American Network (ZikaPLAN; 734584, to Dr. Brickley).BACKGROUND Prenatal exposure to Zika virus has potential teratogenic effects, with a wide spec- trum of clinical presentation referred to as congenital Zika syndrome. Data on survival among children with congenital Zika syndrome are limited. METHODS In this population-based cohort study, we used linked, routinely collected data in Brazil, from January 2015 through December 2018, to estimate mortality among live-born children with congenital Zika syndrome as compared with those without the syndrome. Kaplan–Meier curves and survival models were assessed with ad- justment for confounding and with stratification according to gestational age, birth weight, and status of being small for gestational age. RESULTS A total of 11,481,215 live-born children were followed to 36 months of age. The mortality rate was 52.6 deaths (95% confidence interval [CI], 47.6 to 58.0) per 1000 person-years among live-born children with congenital Zika syndrome, as com- pared with 5.6 deaths (95% CI, 5.6 to 5.7) per 1000 person-years among those without the syndrome. The mortality rate ratio among live-born children with congenital Zika syndrome, as compared with those without the syndrome, was 11.3 (95% CI, 10.2 to 12.4). Among infants born before 32 weeks of gestation or with a birth weight of less than 1500 g, the risks of death were similar regardless of congenital Zika syndrome status. Among infants born at term, those with con- genital Zika syndrome were 14.3 times (95% CI, 12.4 to 16.4) as likely to die as those without the syndrome (mortality rate, 38.4 vs. 2.7 deaths per 1000 person- years). Among infants with a birth weight of 2500 g or greater, those with con- genital Zika syndrome were 12.9 times (95% CI, 10.9 to 15.3) as likely to die as those without the syndrome (mortality rate, 32.6 vs. 2.5 deaths per 1000 person- years). The burden of congenital anomalies, diseases of the nervous system, and infectious diseases as recorded causes of deaths was higher among live-born children with congenital Zika syndrome than among those without the syndrome. CONCLUSIONS The risk of death was higher among live-born children with congenital Zika syn- drome than among those without the syndrome and persisted throughout the first 3 years of life. (Funded by the Ministry of Health of Brazil and others.)