Abstract: Background: High rate of under-five mortality (UFM) in Nigeria is an impediment to national development. This study examined the influence of family type and ethnicity on UFM. Data Source and Methods: The study was cross-sectional and employed the 2013 Nigeria Demographic and Health Survey dataset. The survey utilised a stratified three-stage cluster sampling procedures in interviewing 31,828 women of childbearing age. Data were analysed using Chi-square test, Brass and Cox-proportional hazard models. Results: UFM rates were 92, |19 and 196 deaths per 1000 live births among Yoruba, lgbo/lbo and Hausa/Fulani respectively. On overall, single-parent who were Hausa/Fulani women reported the highest deaths (265/'000) and the polygamous Igbo women reported the lowest (2/'000). UFM is lowest among the lgbo/Ibo while single parenting impact on UFM more among Hausa/Fulani than other ethnic groups. Conclussion: Family type and ethnicity were associated with UFM. Measures to reduce UFM should target single-parenting and the Hausa/Fulanis Keywords: Ethnic groups, Family Type, Mortality, Nigeria