Understanding the factors that influence the use of evidence-based practices (EBPs) for autism spectrum disorder (ASD) in schools is critical to the selection of effective implementation strategies to support their sustained use. The current study has 2 aims: (a) evaluate the association between school leadership profiles (undifferentiated and optimal) and fidelity of EBP implementation and (b) examine the role of implementation climate as a mediator in this association. Participants included 56 principals, 90 special education teachers, and 133 classroom staff from 66 elementary schools. Participants completed the Multifactor Leadership Questionnaire and Implementation Climate Scale. Teachers and staff reported on intensity (frequency) of EBP delivery, and the research team rated the accuracy (adherence) to the components of the EBP. Schools were required to implement at least 1 of 3 EBPs for ASD (discrete trial training, pivotal response training, or visual supports). Using structural equation modeling, we found that schools with optimal leadership had higher observed ratings of teacher and staff fidelity for pivotal response training accuracy (p < .05), but not for discrete trial training or visual supports. However, this association became nonsignificant with the introduction of implementation climate into the models. Optimal leadership profiles were linked to more positive teacher/staff-reported implementation climate, compared with undifferentiated profiles (p < .01), but found no association between implementation climate and fidelity. Overall, the results of this study indicate that the role of principal leadership in EBP implementation is complex, which has implications for fostering a conducive organizational implementation context in schools. (PsycInfo Database Record (c) 2020 APA, all rights reserved).