This case study addressed the problem of implementing response to intervention (RTI) in general secondary education. To investigate this problem, one north Texas school's RTI implementation was examined using the theoretical framework of the concerns-based adoption model (CBAM) and defining RTI as the innovation. RTI-related practices were studied for 10 secondary teachers, two from each core subject (i.e., mathematics, English language arts, science, and social studies) and the fine arts who had been implementing RTI for several years. Data regarding participants' stages of concern about and levels of use of RTI were collected across three time intervals using the three diagnostic instruments of CBAM (i.e., Stages of Concern Questionnaire, Levels of Use interviews, and Innovation Configuration Checklist matrix), behavioral observations during instruction and RTI meetings, and structured exit interviews of participants. Overall, findings indicated that the secondary teachers were at similar stages of concern and levels of use of RTI. Teachers' RTI concerns scores remained highest in the Self phase and lowest in the Impact phase of concern at all three intervals of data collection. As levels of RTI use increased, observed RTI use increased; however, teachers' RTI levels of use scores remained in the early levels of RTI implementation at all three intervals of data collection. Patterns in teachers' responses during exit interviews suggested that contextual factors unique to this setting (e.g., unexpected changes in RTI protocol, priorities of administrative personnel, and demands placed on teachers) may have influenced teachers' concerns about the teacher's role in, the professional development in, and the sustainability of RTI as an innovation. The literature does not currently address secondary teachers' concerns about and levels of use of RTI in relation to CBAM. Therefore, this study not only fills a gap in literature but also has implications for how teachers are trained and supported in implementing and sustaining the practices of consultation and differentiated instruction associated with RTI. This case study provided insight about the importance and value of teachers' participation and knowledge of RTI to facilitate the change process successfully.