The Teacher–Child Interaction Training-Universal (TCIT-U) is a professional development program for teachers that promotes positive relational interactions and strengthens classroom management. This study examines the implementation of TCIT-U in a public school district to guide future implementation and sustainability. This study uses qualitative methods to examine the implementation of TCIT-U across preschool through second-grade classrooms in a suburban public school district in Illinois, United States. Eight teachers and five coaches participated in focus groups, while three administrators completed interviews. Qualitative data from focus groups and interviews are supplemented by quantitative data on satisfaction, teacher sense of efficacy, teacher observations, and school records. Results demonstrated high levels of acceptability, good feasibility, high satisfaction, and several notable improvements across teachers and students, such as improved teachers' confidence and self-efficacy in managing classrooms. Nevertheless, there were implementation challenges, including timing, competing demands, and district priorities. The results from this study offer guidance for future implementation of TCIT-U as an acceptable, feasible, and universal intervention. (author abstract)