Schools are the primary setting in which autistic youth receive intervention, yet fidelity to implementation of evidence-based practices (EBPs) for autism in schools varies. Fidelity is an important metric to determine whether educators are delivering EBPs as designed, and there are many different factors that predict fidelity to EBP implementation. This qualitative study used Domitrovich et al.' (2008) multilevel framework to explore individual- and school-level factors that facilitated or impeded EBP implementation for autistic students in elementary schools. Semi-structured interviews with 26 special education teachers with high and low fidelity implementation of three EBPs for autism (discrete trial training, pivotal response training, and visual schedules) and 26 administrators in schools explored multiple stakeholders' perspectives of the implementation process. Thematic analysis revealed factors from the individual- to the macro-level that influenced teachers' implementation fidelity. Many of these factors are malleable and represent targets for implementation strategies to improve the use of EBPs for autistic students in schools. [This is the in press version of an article published in "International Review of Research in Developmental Disabilities" (ISSN 2211-6095).]