Purpose – The purpose of this paper is to report on a process evaluation of a randomised controlled trial (RCT) intervention study that tested the effectiveness of classroom- and simulation-based crew resource management courses, alone and in combination, and identifies organisational barriers and facilitators to implementation of team training programmes in healthcare. Design/methodology/approach – The RCT design consisted of a before and after study with a team training intervention. Quantitative data were gathered on utility and affective reactions to training, and on teamwork knowledge, attitudes, and behaviours of the learners. A sample of participants was interviewed at the conclusion of the study. Interview responses were analysed, alongside qualitative elements of the classroom course critique, to search for evidence, context, and facilitation clues to the implementation process. Findings – The RCT method provided scientifically robust data that supported the benefits of classroom training. Qualitative data identified a number of facilitators to implementation of team training, and shed light on some of the ways that learning was diffused throughout the organisation. Barriers to successful implementation were also identified, including hospital time and resource constraints and poor organisational communication. Originality/value – Quantitative randomised methods have intermittently been used to evaluate team training interventions in healthcare. Despite two decades of team training trials, however, the authors do not know as well as the authors would like what goes on inside the “black box” of such RCTs. While results are usually centred on outcomes, this study also provides insight into the context and mechanisms associated with those outcomes and identifies barriers and facilitators to successful intervention implementation.