Secondary students with disabilities (SWDs) require evidence-based practices that promote their academic success. However, secondary teachers may feel unprepared to support secondary SWDs, which may reduce their likelihood of implementing evidence-based practices. Therefore, the authors investigated the influence of several preservice and in-service support factors on general and special education teachers' perceived knowledge of evidence-based methods and where to access information on effective methods for serving secondary SWDs in the United States. Their secondary analysis revealed that multiple factors are associated with higher levels of perceived knowledge, such as participation in teacher preparation programs with an adequate focus on SWDs, regardless of teacher type. However, other factors, such as special education certification, were not related to teachers' perceived knowledge. Given the influence of perceived knowledge on teacher implementation, these findings have important implications for researchers, teacher educators, and school and district administrators.