Function-based assessments and interventions are routinely used in school settings as an effective method to address problem behaviors that impede the learning of the student or others. When function-based interventions are not successful, it is often due to problems with treatment integrity (TI). Using an ABCBC single subject design, this study examined whether function-based teacher supports could improve TI. The results demonstrated that the function-based supports provided to the teacher resulted in higher levels of TI and improvements in student behavioral outcomes. Using function-based intervention concepts to develop teacher intervention support, limitations to the study, and directions for future research are discussed.