IntroductionResearch supervisors are uniquely positioned to recognise student abilities and needs. This mixed methods study explores how research supervision can support counselling, psychotherapy and counselling psychology doctoral students in their development of new knowledge, with diversity‐related opportunities and challenges in mind.MethodsGuided by ‘dialectical pragmatism’, we used a semi‐qualitative online survey, Reflective Online Practitioner Survey (ROPS; McBeath, 2020), with closed and open questions disseminated across learning institutes in the UK, Europe and North America.ResultsThe survey received 105 responses, with 45 coming from research supervisors and 60 from research students. Only a minority considered their own research supervision team to be diverse, and two‐thirds of respondents did not see matters relating to diversity and inclusion receiving sufficient emphasis in published research.ConclusionsBoth our quantitative and qualitative data addressed unequal representations in terms of gender and sexuality, ethnicity and heritage, (dis‐)ability and social class—several referring to a ‘history of domination by white, cis, non‐disabled male perspectives’. Many described ‘diversity being left out of research’ with consequences on the capacity to meet clients' need in clinical practice. As one said: ‘we need to decolonise the training material by critically analysing and situating knowledge and calling out missing voices’. Another stated: ‘If the research we conduct and draw on as practitioners cannot actively reckon with oppression within…we risk furthering the violence that marginalised clients, practitioners, and researchers face’. Support and training of supervisors to address diversity and power in research from the start of supervision were argued as essential, with both the supervisory relationship and innovative epistemological angles to knowledge and ‘reality’ in the field of mental health in mind.