To understand whether a responsive parenting intervention for socially disadvantaged mothers was related to preintervention parenting resources, the authors examined both of these conditions as moderators of behavior change in 264 participating families (term, n = 120; very low birth weight, n = 144). Families were randomly assigned to an intervention that targeted responsive behaviors or received developmental information. Limited internal resources, particularly higher levels of anger/hostility, were related to less positive change for the broadest range of responsive behaviors for mothers in the information-only condition but not those in the intervention. Decreased social support moderated less change in provision of rich language input. A systematic session format and parent facilitator may be keys to understanding why a responsive parenting intervention can be effective in spite of limited parental resources.