Background: Trauma-informed (TI) approach is a framework for a system change intervention that transforms the organisational culture and practices to address the high prevalence and impact of trauma on patients and healthcare providers and prevent re-traumatisation in healthcare services. Our systematic review of TI approaches in primary and community mental healthcare identified limited evidence for its effectiveness in the UK, despite endorsement in various policies. We aimed to explain the evidence-policy gap by analysing how and why TI approaches are represented, understood, and implemented in the UK.Methods: A qualitative study comprising of a document analysis of UK health policies followed by semi-structured interviews with key informants with direct experience of developing and implementing TI approaches. We used the Ready Extract Analyse Distil (READ) approach, and framework method.Results: We analysed 25 documents and interviewed 11 professionals from healthcare organisations and local authorities. Policies from healthcare organisations, local authorities, and Scottish and Welsh governments recommended TI approaches. However, there was no UK-wide strategy, agreed terminology and framework, or robust evidence base. Despite growing endorsement of TI approaches in policies, positive statements were not backed up with legislation, funding or resource allocation. Documents and interviews revealed differing understandings of TI approaches between geographical areas and across services, with disconnected, piecemeal implementation. Professionals explained the current landscape of TI approaches by the lack of high-level strategy and leadership, a need for adequate evaluation funding, and a lack of understanding of the term, existing frameworks and evidence available. They wanted more coordination and collaboration between organisations and regions. We identified factors that affected implementation of TI approaches at the level of organisation (leadership support, bottom-up and top-down development, presence of systemic thinking, organisational culture, resource allocation, competing priorities) and wider context (government support, funding, impact of the COVID-19 pandemic). Professionals had conflicting views on the future of TI approaches, however all agreed that government backing is essential for implementing policies into practice.Conclusions: A coordinated, centralised strategy on TI approaches in health systems, improved funding for evaluation, and education through professional networks about evidence-based TI health systems can increase value and reduce waste in research and implementation of TI approaches in the UK.