State and national educational leaders encourage the use of an integrated multitiered system of supports (MTSS) to improve services to students with academic and social behavior problems. Implementing and sustaining MTSS is facilitated by support from leaders in state education agencies (SEAs). The purpose of this study was to identify the specific events, resources, and supports that help or hinder the work of scaling up an integrated MTSS approach from the perspective of MTSS leaders in SEAs. Researchers interviewed leaders in 27 U.S. states using the critical incident technique, a qualitative methodology to identify critical incidents associated with changes in practice. Eight helping incident, seven hindering incident, and nine "wish list" categories were identified. Helping categories included multidisciplinary leadership, access to professional development, consistent language and/or practices, consultation with external partners, and a focus on student outcomes in evaluation and planning. Seven hindering categories included competing philosophies, high personnel turnover, varying levels of readiness, and inadequate data systems. Participants also identified two unique categories associated with the items they wished had happened or could happen in the future including access to personnel with high-level MTSS training and access to more effective interventions.