This study reports the results of a randomized trial of a parent engagement intervention (the Getting Ready Project) on directly observed learning-related social behaviors of children from families of low-income in the context of parent-child interactions. The study explored the moderating effect of parental depression on intervention outcomes. Participants were 204 children and their parents, and 29 Head Start teachers. Semi-structured parent-child interaction tasks were videotaped two times annually over the course of two academic years. Observational codes of child behaviors included agency, persistence, activity level, positive affect, distractibility, and verbalizations. Controlling for gender and disability concerns, relative to children in the control group, those in the treatment condition experienced a significant decline in activity level. Furthermore, compared to children of non-depressed mothers and to control children, those in the experimental condition whose parent reported elevated levels of depression showed greater gains in positive affect and in verbalizations.