The study employed a developmental, ecological, and resiliency framework to examine whether interactive peer play competencies mediated associations between teacher reported problem behavior and learning outcomes for a representative sample of urban low-income children (N = 507 across 46 Head Start classrooms). Structural equation models provided evidence for full mediation, whereby associations between internalizing and externalizing problem behavior and learning outcomes were fully explained through their effects on interactive peer play skills. An alternate model was also tested (whether problem behavior mediated the effects of interactive peer play on spring learning outcomes); however, this alternate model was not supported in these data. A third model testing whether mediation was conditional on child sex was also not supported. Implications for developmental theory, research, and practice are discussed as they relate to opportunities to build on children's strengths and promote learning within early childhood educational programs serving children living in urban poverty. (Contains 2 figures and 5 tables.)