Most foster parents in the United States are required to participate in training, yet no empirical support exists for the training's effectiveness. During the past two decades, high-quality clinical trials have documented that parent management training (PMT) programs produce positive outcomes for children and families in clinical and school settings; yet, these advances have not transferred to foster/kinship parents. Here, we describe a randomized control trial testing the effectiveness of a PMT-based treatment with 700 foster/kinship parents in San Diego County. The collaborative processes to engage stakeholders, the strategies for involving parents, and the results of two levels of developer involvement in training and supervision on child behavioral outcomes are also described. (Contains 2 tables and 1 figure.)