A growing number of research studies are attempting to increase access to naturalistic developmental behavioral interventions (NDBIs) for autistic toddlers and their families by translating these approaches into Part C Early Intervention systems. As efforts to increase the use of NDBIs across EI systems grow, it is important to expand the scope of research to evaluate the implementation impact of this work. In order to address this gap, the current study was grounded in the Reach, Effectiveness, Adoption, Implementation, and Maintenance framework (RE-AIM) to evaluate a broader range of implementation outcomes when a parent-mediated NDBI, Project ImPACT, was implemented within an Early Intervention system. Specific aims included examining: 1) the reach of Project ImPACT to children across the system; 2) the perceived effectiveness of Project ImPACT; 3) rates of provider participation in Project ImPACT training and consultation; 4) the delivery and adaptation of Project ImPACT by Early Intervention providers; and 5) providers’ intent to sustain their use of Project ImPACT. Forty-eight Early Intervention providers enrolled in Project ImPACT training, with a subsample participating in ongoing group consultation followed by an exit interview and a 6-month follow-up survey. Although there was a high level of interest in Project ImPACT training and good retention once enrolled, only half of EI providers who expressed interest in Project ImPACT training ultimately enrolled. Participating providers delivered Project ImPACT to families and children who were representative of state-level demographic information and perceived that Project ImPACT was effective for families and children on their caseload irrespective of whether children were autistic. Consistent with other research studies, providers’ fidelity to Project ImPACT was inconsistent, and providers reported a moderate level of adaptation to the program. At 6-month follow-up, providers reported high maintenance of Project ImPACT. The findings from this study have implications for how the RE-AIM framework could be used to more concisely characterize the impact of implementation efforts within public systems serving autistic toddlers and their families.