【Background】Despite promising findings regarding the safety, fidelity, and effectiveness of peer-delivered behavioral health programs, there are training-related challenges to the integration of peers on health care teams. Specifically, there is a need to understand the elements of training and consultation that may be unique to peer-delivered interventions.【Methods】As part of a pilot effectiveness-implementation study of an abbreviated version of Skills Training in Affective and Interpersonal Regulation (STAIR) for posttraumatic stress disorder (PTSD), we conducted a mixed-methods process evaluation utilizing multiple data sources (questionnaires and field notes) to characterize our approach to consultation and explore relations between fidelity, treatment outcome, and client satisfaction.【Results】Peer interventionists exhibited high fidelity, defined by adherence (M = 93.7%, SD = 12.3%) and competence (M = 3.7 "competent," SD = 0.5). Adherence, β = .69, t(1) = 3.69, p < .01, and competence, β = .585, t(1) = 2.88, p < .05, were each associated with trial participant's satisfaction, but not associated with clinical outcomes. Our synthesis of fidelity-monitoring data and consultation field notes suggests that peer interventionists possess strengths in interpersonal effectiveness, such as rapport building, empathy, and appropriate self-disclosure. Peer interventionists evidenced minor challenges with key features of directive approaches, such as pacing, time efficiency, and providing strong theoretical rationale for homework and tracking.【Conclusion】Due to promise of peers in expanding the behavioral health workforce and engaging individuals otherwise missed by the medical model, the current study aimed to characterize unique aspects of training and consultation. We found peer interventionists demonstrated high fidelity, supported through dynamic training and consultation with feedback. Research is needed to examine the impact of consultation approach on implementation and treatment outcomes.【Plain language summary】Peers-paraprofessionals who use their lived experiences to engage and support the populations they serve-have been increasingly integrated into health care settings in the United States. Training peers to deliver interventions may provide cost savings by way of improving efficient utilization of professional services. Despite promising findings in regard to safety, intervention fidelity, and effectiveness of peer delivery, there are important challenges that need to be addressed if peers are to be more broadly integrated into the health care system as interventionists. These include challenges associated with highly variable training, inadequate supervision, and poor delineation of peer's roles within the broader spectrum of care. Thus, there is a need to understand the unique components of training and consultation for peers. We report key findings from an evaluation of a pilot study of an abbreviated version of Skills Training in Affective and Interpersonal Regulation (STAIR) for posttraumatic stress disorder (PTSD), adapted for peer delivery. We characterize our approach to consultation with feedback and explore relations between fidelity, treatment outcome, and client satisfaction. Our study extends the small yet growing literature on training and consultation approaches to support fidelity (adherence and competence) among peer interventionists. Organizations hoping to integrate peers on health care teams could utilize our fidelity-monitoring approach to set benchmarks to ensure peer-delivered interventions are safe and effective.