Background: Neonatal mortality rate is an important health index. The present study was conducted to determine the mortality rate and its causes in neonatal intensive care units (NICUS) in Iran. Methods: Online search was done without time limit until June 2018 in several databases, such as PubMed, Web of Science (ISI), Scopus, Magiran, Barakat Knowledge Network System, SID, Iranian National Library, Regional Information Center for Science and Technology (RICST), Google Scholar search engine, and Iranian journals. The articles were qualitatively assessed after evaluating the inclusion and exclusion criteria. The Cochran's Q test and I2 index were used to determine the heterogeneity between studies. Meta-analysis was done based on a random effects model using Comprehensive Meta-Analysis Software (version 2). Results: Thirty-one eligible studies were analyzed. The mortality rate in 24,995 neonates admitted to NICUs in Iran was estimated to be 11.40%(95% CI: 9.10-14.20). The lowest mortality rate reported as 7.70%(95% CI: 6.01-9.82) was related to the Center of Iran, and the highest mortality rate was reported as 19.26%(95% CI: 15.82-23.24) in the west of Iran. In this regard, the difference was statistically significant (P< 0.001). The most common causes of mortality in NICUs in Iran were prematurity (44.14%[95% CI: 31.95-57.08]), respiratory distress syndrome (RDS)(31.93%[95% CI: 22.83-42.66]), congenital malformation (16.09%[95% CI: 12.85-19.95]), septicemia (12.66%[95% CI: 8.87-17.75]), and asphyxia (7.58%[95% CI: 4.63-12.19]).

Conclusion: The most common causes of mortality in Iranian neonates were prematurity, RDS, and congenital anomalies. We also found the mortality rate to be acceptable (11.4%). To reduce the mortality rate, we recommend performing prenatal screening tests and genetic counseling. In addition, maternal care during pregnancy should be improved to reduce premature delivery.