Background In India, excess female under-5 mortality is well documented. Under-5 mortality is also known to be patterned by socioeconomic factors. This study examines sex differentials and sex-specific wealth gradients in neonatal, postneonatal and child mortality in India.

Methods Repeated cross-sectional study of nationally representative samples of 298 955 children 0–60 months old from the National Family Health Surveys conducted in 2005–2006 and 2015–2016. The study used logistic regression models as well as Cox proportional hazards models.

Results Overall, boys had greater neonatal mortality than girls and the difference increased between 2005–2006 and 2015–2016. Girls had greater postneonatal and child mortality, but the difference decreased between the surveys and was not statistically significant for child mortality in 2015–2016. A negative wealth gradient was found for all mortality outcomes. Neonatal mortality was persistently greater for boys. Girls had higher child mortality than boys at low levels of wealth and greater postneonatal mortality over much of the wealth distribution. The wealth gradient in neonatal mortality increased between surveys. Females had a stronger wealth gradient than boys for child mortality.

Conclusion Not distinguishing between neonatal, postneonatal and child mortality masks important gender-specific and wealth-specific disparities in under-5 mortality in India. Substantial gains towards the Sustainable Development Goals can be made by combating neonatal mortality, especially at low levels of wealth. Although impressive improvements have been made in reducing the female disadvantage in postneonatal and child mortality, concerted engagements are necessary to eliminate the gender gap—especially in poor households and in north India.