This paper compares unitary and collective models of investment in children in the context of a polygynous family structure (with multiple wives) using a Living Standards Measurement Survey from Côte d’Ivoire. I examine whether the mother’s rank (whether she is a senior (first) or junior wife) in the household and her characteristics relative toother wives influence her child’s school enrollment, school expenditures and anthropometric measures. The findings with respect to the anthropometric measures ofchild well-being are not inconsistent with the assumptions of the unitary model.However, I find evidence that being the child of a junior wife negatively affects enrollment and school expenditures at the middle school ages, relative to being the child of a senior wife, although it slightly raises expenditures at the primary school ages. Theresults of fixed effects regressions which take account of unobserved heterogeneity of thefathers are consistent with the evidence of the OLS estimates although imprecisely estimated. This evidence that rank affects investments in children is consistent with the credit- constrained collective model presented in the paper.