We conducted a school-wide training for Japanese preschool teachers based on the behavioral and functional approach to children with problem behaviors. Twenty-five Japanese teachers at a kindergarten and nursery school participated in the program, attending six training sessions and four case-study meetings. The training sessions consisted of (a) lectures on behavioral and functional approaches and (b) group work to develop individual support plans. Following training, improvement was seen in both teachers' knowledge of applied behavior analysis as well as children's behaviors targeted in the training plans. In addition, the overall behavior of the children improved, and the postprogram questionnaire showed that participants' satisfaction and acceptance were high. A case-study meeting had been maintained weekly at both schools for 1 year. Although these results are promising, the current investigation has limitations, and the results should be interpreted with caution.