Introduction: Premature death or death during the beginning part of life is the major cause of concern for the research. As far as living and socioeconomic conditions of a country or society are concerned, infant and child mortality is considered a sensitive indicator. Also, child mortality continues to be a major public health issue particularly in developing countries where it is mostly concentrated and keeps occurring in large numbers. In India, the burden of children dying under five years of age is dispropor tionately carried by socially disadvantaged groups. Mortality under age three has special importance because the child in this developing world is vulnerable to infectious diseases. Objective: The present study is an attempt to examine the factors that affect on mortality of children under age three in the most populous state of India. Methods: In this study, we have utilized the data from the fourth round of the National Family Health Survey (NFHS), conducted in 2015-2016 for Uttar Pradesh. Bivariate analysis of data and unadjusted/adjusted logistic regression has been used in the present study to know the likelihood of the various factors. Results: Logistic regression suggests that, among the socio-demographic variables, women__ampersandsignrsquo;s education emerges as a strong predictor for explaining mortality under age three. As expected, the child of the illiterate mothers has experienced higher mortality as compared with literate mothers. Children of households with poor wealth index and sorter preceding birth interval are more likely to die than their counterparts. Mother__ampersandsignrsquo;s age at childbirth and birth order also plays a significant association in underage three mortality. Male children have almost the same risk of dying as female children. Conclusion: The study indicates mother__ampersandsignrsquo;s age at birth, education, birth order, birth interval and basic immunization emerges as an important factor to influence child mortality under age three, therefore there is an earnest need to intervene in these issues in the society.