Breastfeeding provides essential nutrients for newborn growth and development and bioactive factors for protection against childhood illnesses. In addition, some studies have linked breastfeeding to improved educational outcomes. The evidence supporting the benefit of breastfeeding on educational outcomes is largely from high-income countries, where socioeconomic status is strongly correlated with breastfeeding behaviour. It has been hypothesised that the positive effect of breastfeeding observed in high-income countries is a manifestation of socioeconomic status advantage, not the biological effect of breastfeeding. Evidence from sub-Saharan Africa, where socioeconomic status is not a strong predictor of breastfeeding, could clarify this association, but studies from sub-Saharan Africa are scarce in this debate. In this thesis, I investigated whether the duration of breastfeeding in infancy is associated with educational attainment at school age in sub-Saharan Africa. The thesis is centred on two themes. Theme one examined the socioeconomic pattern of breastfeeding in sub-Saharan Africa based on data from six repeated cross-sectional surveys in Ghana and six longitudinal cohorts in Ethiopia, Malawi, Uganda, and Zambia. Theme two, the primary research question, investigated the association between breastfeeding duration and educational outcomes in sub-Saharan Africa through a systematic review of the existing literature on the research question and analysis of longitudinal data from cohorts in Malawi and Uganda. Educational attainment was measured as age-for-grade based on a child’s expected primary school grade at each age. Key potential co founders, including paternal and maternal socioeconomic status and HIV status, were adjusted for. The meta-analysis of the six cohorts and the pooled analysis of the data from Ghana both showed no clear socioeconomic pattern in breastfeeding. The systematic review of the association between breastfeeding and educational outcomes revealed that only two studies had investigated the association in sub-Saharan Africa before this thesis. Both studies found no conclusive evidence to support an association between breastfeeding and educational outcomes. In the analysis of longitudinal data from Uganda, I found no evidence of an association between duration of any breastfeeding and educational attainment. However, in Malawi, I found that exclusive breastfeeding for six months reduced the odds of being over-age for grade in primary school and falling behind in early school grades compared to exclusive breastfeeding for less than three months. Meta-analysis combining estimates from Malawi and those from a previous study conducted in South Africa that was identified through the systematic review also showed that exclusive breastfeeding for six months reduced the odds of repeating a grade compared to exclusive breastfeeding for less than two months. These findings indicate that exclusive breastfeeding for two to six months may improve educational attainment, but further sub-Saharan Africa studies are needed to provide a broader understanding of the association, as the evidence is still limited. Additionally, the findings suggest that the improved educational outcomes observed among exclusively breastfed children in high-income countries may not be entirely attributable to socioeconomic confounding.