This study examines the generalizability of Reformulated Emotional Security Theory (EST-R) among a large and diverse sample of low-income, unmarried parents with young children (n=5,100). Path analysis indicated that child emotional insecurity mediated the relation between destructive conflict (i.e., moderate negative conflict between parents) and child behaviour problems, and mediated the relation between intimate partner violence (IPV; i.e., severe negative conflict between parents) and child behaviour problems. Although destructive conflict and IPV shared this mechanism, destructive conflict had a direct effect on child behaviour problems, whereas IPV did not. Child emotional insecurity did not mediate the link between constructive conflict and behaviour problems. These results indicate that the EST-R is generalizable to vulnerable families with young children. Furthermore, results suggest that destructive conflict and IPV have unique effects on child emotional insecurity and behaviour problems.