Foster care faces serious challenges, such as behavioral problems in foster children and parental stress and ineffective parenting behavior in foster parents. The results of a pilot study that evaluated a training program for foster parents based on nonviolent resistance are described. In a pretest-posttest design, data were collected from 25 families. Significant reductions in externalizing, internalizing, and total problem behavior in the foster children and in parenting stress were found. Using a reliable change index, significant improvements in externalizing, internalizing, and total problem behavior were found in, respectively, 72, 44, and 80% of the cases. Most improvements proved to be clinically relevant. Effect sizes ranged from medium to large for problem behavior, and from small to medium for parenting stress.