BackgroundEvidence-based interventions, which are typically supported by data from randomized controlled trials (RCTs), are highly valued by providers of human services like child welfare. However, implementing such interventions in the context of a randomized clinical trial is a complex process, as conducting an RCT adds extra tasks for providers and complicating factors for provider organizations. Utilizing the Exploration, Preparation, Implementation, and Sustainment Framework, this study examines factors that facilitate or impede success in the implementation of evidence-based interventions in the context of a largescale trial of SafeCare,® a child maltreatment intervention.MethodsQualitative data were obtained as part of a larger mixed-methods study involving a cluster randomized trial comparing SafeCare to usual services for caregivers within nine child welfare agencies across four states. Between May and October 2017, individual interviews were conducted with a purposive sample of 21 child welfare administrators and 24 supervisors, and 19 focus groups were conducted with 84 providers. Data were coded iteratively and grouped into themes.ResultsSeveral interconnected themes centered on facilitators and barriers to SafeCare implementation in the context of a randomized clinical trial. Facilitators included: (1) Benefits afforded through RCT participation; (2) Shared vision and sustained buy-in across system and organizational levels; and (3) Ongoing leadership support for SafeCare and the RCT. Barriers that hindered SafeCare were: (1) Insufficient preparation to incorporate SafeCare into services; (2) Perceived lack of fit, leading to mixed support for SafeCare and the RCT; and (3) Requirements of RCT participation at the provider level.ConclusionsThese data yield insight into an array of stakeholder perspectives on the experience of implementing a new intervention in the context of a largescale trial. This research also sheds light on how the dynamics of conducting an RCT may affect efforts to implement interventions in complex and high-pressure contexts. Findings highlight the importance of aligning knowledge and expectations among researchers, administrators of organizations, and supervisors and providers. Researchers should work to alleviate the burdens of study involvement and promote buy-in among frontline staff not only for the program but also for the research itself.