Objective: We conducted a within intervention group analysis to test whether caregiver engagement (e.g., participation, homework completion, openness to ideas, apparent satisfaction) in a group-based intervention moderated risk factors for foster child outcomes in a state-supported randomized trial of caregiver parent training. Methods: The intervention was delivered in 16 weekly sessions by trained leaders. Outcomes were pre-post change in problem behaviors and negative placements. Results: Analysis of 337 caregivers nested within 59 parent groups showed caregiver engagement moderated number of prior placements on increases in child problem behaviors, and moderated risk of negative placement disruption for Hispanics. Conclusions: Variance in parent group process affected program effectiveness. Implications for practice and increasing effective engagement are discussed.