BackgroundOut-of-hospital Emergency Medical Services (OHEMS) require fast and accurate assessment of patients and efficient clinical judgment in the face of uncertainty and ambiguity. Guidelines and protocols can support staff in these situations, but there is significant variability in their use. Therefore, the aim of this study was to increase our understanding of physician decision-making in OHEMS, in particular, to characterize the types of decisions made and to explore potential facilitating and hindering factors.MethodsQualitative interview study of 21 physicians in a large, publicly-owned and operated OHEMS in Croatia. Data was subjected to an inductive content analysis.ResultsPhysicians (mostly young, female, and early in their career), made three decisions (transport, treat, and if yes on either, how) after an initial patient assessment. Decisions were influenced by patient needs, but to a greater extent by factors related to themselves and patients (microsystem), their organization (mesosystem), and the larger health system (macrosystem). This generated a high variability in quality and outcomes. Participants desired support through further training, improved guidelines, formalized feedback, supportive management, and health system process redesign to better coordinate and align care across organizational boundaries.ConclusionsThe three decisions were made complex by contextual factors that largely lay outside physician control at the mesosystem level. However, physicians still took personal responsibility for concerns more suitably addressed at the organizational level. This negatively impacted care quality and staff well-being. If managers instead adopt a learning orientation, the path from novice to expert physician could be more ably supported through organizational demands and practices aligned with real-world practice. Questions remain on how managers can better support the learning needed to improve quality, safety, and physicians’ journey from novice to expert.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12873-023-00830-w.