An increasing number of older people with severe mental illness (SMI) poses additional challenges to healthcare and social services. This scoping review aimed to investigate the life situation of older people living with severe mental illness and identify the research gaps in the existing literature. The current review followed the methodological framework for conducting scoping reviews by Arksey and O'Malley, consisting of five main stages: (1) identifying the research question (2) identifying relevant studies, (3) selecting the studies, (4) charting the data, and (5) collating, summarising, and reporting the results. An optional sixth stage, a consultation exercise, has also been used in this study: The scoping review was conducted in accordance with the PRISMA extension for scoping reviews PRISMA-ScR, and the databases PsychINFO Scopus, Cinahl, Web of Science and PubMed were used. A total of 24 studies were included in the review. The thematic analysis focused on: (1) the perspective of older people with SMI, (2) the perspective of healthcare professionals supporting older people with SMI, and (3) the perspective of informal carers supporting older people with SMI. The results describe the life situation of older people living with SMI, especially in relation to the older peoples' experiences of suffering and well-being. The staff and the informal carers need adequate knowledge to provide support to the older people with SMI. To gain greater knowledge about the life situation and support needed by older people with SMI, we strongly advocate additional research focusing on their own experiences.