Questions: What perceptions do physiotherapists have about their role in managing the physical health of people with severe and persistent mental illness (SPMI)? What are the barriers to treating physical health conditions in this clinical population, and what enablers may improve access to physiotherapy services? Design: Mixed-methods research design combining focus groups, interviews and an online survey. Participants: Eighty-eight Australian registered physiotherapists: 31 in the focus groups and interviews (mean age 32 years, 68% female) and 57 in the survey (mean age 38 years, 86% female). Methods: Focus groups and interviews explored participants' understanding of mental illness; their role in managing the physical health of people with SPMI; and the barriers and enablers to service delivery. Key themes were derived using an inductive approach. The survey was used to determine physiotherapists' attitudes and knowledge regarding mental illness; perceived role of physiotherapy in mental health; and need for professional development in the mental health area. Participant characteristics and survey information were analysed using descriptive statistics. Results: Qualitative and quantitative results were confirmatory. Participants indicated that physiotherapists can play a role in the management of physical health conditions in people with SPMI. Participants also stated that such treatment was part of their job, given the extensive evidence that physiotherapy interventions are effective for the comorbidities that are common among people with SPMI. Barriers included: limited education about and confidence in how to manage people with SPMI; health system structure; and stigmatisation of people with SPMI. Conclusion: Physiotherapists are ideally poised to become leaders in managing the physical health of people with SPMI. To improve the physical health in this important yet overlooked population, it is recommended that: physiotherapists take up general mental health training opportunities; undergraduate physiotherapy education increases content in this clinical area; physiotherapy-specific professional development opportunities are developed further; and health system barriers are addressed.