Naturalistic developmental behavioral interventions (NDBIs) are evidence-based interventions for young children with autism spectrum disorder. There has been growing interest in implementing manualized NDBIs within the early intervention (EI) system without a clear understanding of how these programs and the broader strategies encompassed within them are already used by EI providers. This study examined the use of manualized NDBI programs and broader NDBI strategies within an EI system and factors that impacted their use. Eighty-eight EI providers completed a measure of NDBI program and strategy use. Thirty-three providers participated in a supplemental focus group or interview. Overall, providers described using broader NDBI strategies and the need to adapt manualized NDBI programs. Provider-, intervention-, and organization-level factors impacted their use of NDBI programs and strategies.