Income inequality is one of the major underdevelopment problems facing developing countries including Nigeria. Despite serious attention given to inequality in both theoretical and empirical literature, it is still understudied in the case of Nigeria because most empirical studies overaggregate analysis. This study departs from existing studies in two ways. First, the study disaggregates household consumption expenditure into food and nonfood and thus decomposes inequality into within-groups and between-groups components using generalised Entropy (GE) measures. The purpose is to ascertain where inequality in household consumption expenditure is coming from. Second, the study employs regression-based inequality decomposition to ascertain the determinants of inequality in food and nonfood expenditure using household demographic and socioeconomic characteristics as covariates. The data used in the analyses is the 2010 Harmonised Household Living Standards Survey for Nigeria. The results show that nonfood expenditure is the major source of inequality in household consumption expenditure in both urban and rural areas with inequality coefficients of above 0.6 compared to about 0.4 for food expenditure. The decompositions also show that within-group inequalities for nonfood and food expenditure are respectively 0.97 and 0.365 using the Theil index, while between-group inequalities for nonfood and food are respectively 0.016 and 0.035. Furthermore, the regression based inequality decompositions show that variables such as living in rural areas, household size, household dwelling and household dwelling characteristics account for the significant proportion of inequality in food and nonfood expenditure. The policy recommendation of this study, among others, is that policies should focus on addressing inequality within rural and urban areas especially with respect to nonfood expenditure than in inequality existing between urban and rural areas. Some of the nonfood expenditures that need to be paid attention to are expenditure in education, health, energy, accommodation, water and sanitation.