Objectives This study explored the perceptions and attitudes of qualified UK dental therapists (DTs) to act in a diagnostic role in the dental care of paediatric patients. Methods A mixed methods study. An electronic questionnaire was sent out to the members of associations and closed social networking groups for qualified DTs across the UK. The questionnaire explored the training, clinical experience and working practices of the participants and measured their agreements with applicable statements using Likert scale scores. Semi-structured interviews were also undertaken to explore how UK DTs perceived a diagnostic role for them and what barriers and facilitators they experienced. Results A total of 155 questionnaire responses were returned and 11 interviews conducted. Participants were mostly women (94.8%) with a broad range of working experience, with a mean experience of 9.5 years (± 8.8 standard deviation [SD]) (range: 1-42 years). From the questionnaires, when asked to score agreement on a Likert scale from 0-5, DTs agreed that in a diagnostic role, they could increase access to dentistry for patients and a high proportion were in agreement that they had the knowledge to carry out examination (mean = 4.43 ± 0.87 SD), diagnosis (mean = 4.37 ± 0.90 SD) and care planning for paediatric patients (mean = 2.74 ± 1.32 SD). The interviews yielded three qualitative supra themes: 'working in the UK as a DT today'; 'the perceptions of dental therapists on acting in a diagnostic role in paediatric dental care'; and 'barriers and facilitators to acting in a diagnostic role' and within these, eight major themes were identified. Conclusion Within the limitations of a small sample who were representative of the workforce demographic and educational structures, we found that DTs felt that if they were to act in a diagnostic role, it would improve access to dental services benefitting patients, dentists and the DT profession. DTs identified and explored barriers and facilitators to a diagnostic role. Change is required to overcome these barriers in order to support DTs to act in a front-line diagnostic role.