Children with autism spectrum disorders (ASD) are being increasingly included in early childhood settings. As such early childhood teachers need pre-service training to support their knowledge of ASD and preparation to implement evidence-based practices. Mentor teachers and administrators of pre-service clinical sites play an important role in this pre-service training. As such we conducted an explanatory sequential mixed method study to understand how pre-service early childhood teachers' knowledge of ASD, attitudes towards inclusion of children with ASD, perceptions of challenging behaviors, and familiarity with intervention practices was influenced by the amount of coursework completed, number of field experiences, and mentor teacher/administrator perspectives. The study included surveys and follow up interviews with a subset of survey participants. Findings provide important insights into the pre-service preparation of early childhood teachers to support the inclusion of children with ASD including the importance of mentor teachers' and administrators' attitudes towards inclusion, the need to educate pre-service teachers about evidence-based practices, and provide clinical placements that are inclusive of children with ASD. Limitations, practical implications, and recommendations for future research are discussed.