Experts unanimously agree that armed conflict is harmful to children. However, few studies exist that examine the link between armed conflict and language and cognitive development in the early years. This paper uses the Young Lives data from Perú and Ethiopia to analyze the relationship between armed conflict and early language and cognitive development using two standardized measures, the Peabody Picture Vocabulary Test (PPVT) and the Cognitive Development Assessment-Quantitative (CDA-Q), both administered at or near age 5. The results show that after holding a variety of child, family, and community factors constant, living in a region of the country that has experienced war more recently is associated with lower receptive language (PPVT) scores in Perú, while intensity of the conflict is associated with lower PPVT scores in Ethiopia. Attending preschool and higher levels of family wealth are strong predictors of higher PPVT scores. These findings suggest that children living conflict or post-conflict situations are particularly vulnerable to language disadvantages that could impact opportunities throughout the lifespan. Therefore, early childhood development should be prioritized in emergencies and post-conflict reconstruction, with a special emphasis on equity to ensure generations of rural and poor children in conflict-affected areas are given opportunities to thrive.