The Keeping Foster Parents Trained and Supported intervention (KEEP) is one of the few evidence-based programs that has been shown to be effective in reducing behavior problems and failed foster care placements in foster children. During the KEEP intervention’s implementation trial, process-oriented participant engagement (evaluating factors such as participant homework completion, openness to ideas, and level of participation in the group process) was identified as an important moderator of intervention outcomes. However, this evaluation of the relation between engagement and child behavior problems was limited to post-intervention behavior change, limiting the ability to determine at what point(s) during the intervention engagement may be most relevant. In light of these limitations, the present study had two aims: 1) evaluate the relation between the contemporaneous trajectories of process-oriented foster caregiver engagement and child behavior problems using data from each of the 15 content-focused weeks of the KEEP intervention and 2) to determine which pre-intervention factors were most associated with foster caregiver engagement at different time points during the intervention. To address these aims, this dissertation used data from the intervention group (n = 164) from a larger study (KEEP Reaching; N = 354) examining the overall effects of the KEEP intervention. Using piecewise growth curve modeling analyses, the first aim of this study identified a significant upward trajectory for process-oriented engagement and a significant downward trajectory for child behavior problems during the eleventh through fifteenth weeks of the KEEP intervention. Statistical limitations inhibited the planned evaluation of the association between these contemporaneous trajectories. As a result, analyses for the second aim were not supported. Supplementary analyses were conducted in order to determine whether there was an overall association between process-oriented engagement and child behavior problems. When aggregated across all 15 weeks of the intervention, higher levels of process-oriented engagement were associated with fewer child behavior problems. Despite being unable to draw conclusions about the relation between the concurrent trajectories of engagement and child behavior problems, this study was able to demonstrate that there is a relation between these constructs and that they may share a parallel process, which supports continued research in this area.