The present study examined proximal and distal barriers and supports within the Swedish service system that may affect implementation of early and intensive behavioral intervention (EIBI) for children with autism. A case study approach with roots in ethnography was chosen to explore this issue. Two preschools exemplifying "high quality practice" were studied and information was collected through multiple sources during a 12 month period, this included participant observations, direct observations, semi-structured interviews with key informants; paraprofessionals, parents, special educators, habilitation specialists and a focus group interview. Interview transcripts and field notes were combined and analyzed using an abductive grounded theory approach. Findings highlight the relevance of researchers understanding and taking into consideration the effect that distal variables have on implementation within proximal settings. A theoretical model of factors affecting implementation was conceptualised to include: staff entry knowledge and competence, development through supervision, the role of the preschool administrator, as well as distal influences and inter-organizational tensions, values, and bridges. Findings are discussed within the context of implementation science. Implications for future research are discussed as well as areas in need of further development to bridge the gap between research and practice.