INTRODUCTION: People with severe mental illness (SMI) have high rates of physical illnesses. Informal carers are core partners in addressing these issues, however research on their views/experiences is limited and there is no systematic review published on the topic. AIM: This integrative thematic review explored the experiences and views of carers on physical healthcare in SMI by synthesizing the existing qualitative research findings. METHODS: Six databases were searched from 2000 to 2021. Data were extracted and synthesised using thematic integrative analysis. The quality of included studies was assessed with the JBI Critical Appraisal Checklist. RESULTS: Five studies were included. Nine themes were identified conceptualising carers' perceived facilitators, barriers and roles regarding physical healthcare for people with SMI. DISCUSSION: Carers felt that receiving practical help and a specialised role for mental health nurses would facilitate better physical healthcare. Lack of coordination/communication and poor service access/responsiveness were common barriers, often compounded by diagnostic overshadowing. Carers are involved in promoting healthy lifestyles, monitoring physical health and supporting access to services. IMPLICATIONS FOR PRACTICE: Mental health nurses should ensure they are responsive to carers' concerns and proactively support them to promote the physical health of people with SMI.