One avenue for improving children's socio-emotional competence and classroom behavior is by improving the quality of early teacher-child interactions. Universal Teacher-Child Interaction Training (TCIT-U), adapted from Parent Child Interaction Therapy, is a school-based prevention program in which teachers are taught to use the principles of learning and behavior management in the classroom to increase positive interactions and to reduce problem behaviors in young children. The current study advanced prior research by investigating TCIT-U's effectiveness with English language learners and in a rural public school setting. We examined the direct effects on teachers' and children's observed behavior, and the durability of teachers' skill use in the next school year. In the present study, changes in teacher and child behavior were analyzed within a multiple baseline design across two classrooms with five teachers and 39 preschool children. Teacher and child behavior were measured through behavioral observations and a standardized teacher rating scale. Results revealed that teachers increased their use of positive attention and behavior management skills with intervention, and these changes remained stable during follow-up. Further, improvements in children's behavior were detected by significant changes in post-TCIT teacher ratings on a strengths-based measure. Observed disruptive behavior displayed decreasing trends during intervention for children nominated by their teachers as having behavioral concerns, although the overlap and variability in the data limited convincing evidence of an intervention effect. Finally, teachers reported high satisfaction with the program. This study supports TCIT-U's use as an intervention to increase positive interactions between teachers and students and as a universal prevention program for behavior problems in preschool classrooms.