Advancing the long-term prospective study of explanations for the effects of marital conflict on children’s functioning, relations were examined between interparental conflict in kindergarten, children’s emotional insecurity in the early school years, and subsequent adolescent internalizing and externalizing problems. Based on a community sample of 235 mothers, fathers, and children (Ms = 6.00, 8.02, 12.62 years), and multimethod and multireporter assessments, structural equation model tests provided support for emotional insecurity in early childhood as an intervening process related to adolescent internalizing and externalizing problems, even with stringent autoregressive controls over prior levels of functioning for both mediating and outcome variables. Discussion considers implications for understanding pathways between interparental conflict, emotional insecurity, and adjustment in childhood and adolescence.