This paper examines whether the mother’s rank (whether she is a senior or junior wife) in polygamous households in Côte d’Ivoire injects favoritism that could lead to differential investment in children. The concern is that favoritism based on mother’s rank could cause an inefficient allocation of household resources. This question is analyzed employing Ordinary Least Squares on a Living Standards Measurement Survey microdataset collected by the World Bank. An interesting pattern is found: whether the senior or junior children are advantaged depends on the age difference between the senior and junior wife. Senior children are at an advantage when the age gap is small; however, investments in senior children decline as this age gap increases. For example, the child of a senior wife is nearly 4 percentage points more likely to be enrolled in school as the child of a junior wife who is 5 years younger. With an age difference of 15 years, the child of a senior wife is 9 percentage points less likely to be enrolled. Inefficient disparities in investments of polygynous children potentially affect not only the well-being of those children but also Côte d'Ivoire as a society. The finding of disparity in schooling investments speaks to a role for policies that will incentivize more rational allocations to children such as increasing women’s access to credit markets or paying mothers to keep children in school.