A quarter of acute hospital beds are occupied by people with dementia, and a hospital stay may impact negatively on their health and wellbeing. The development and implementation of volunteers to provide social, activity-based, one-to-one support for people with dementia in acute hospitals has become routine practice. However, the evidence to support this practice has not been identified or evaluated. This systematic review considers the effect of volunteers on the care and experience of people with co-morbid cognitive impairment/dementia in acute hospitals. The systematic search identified 444 papers, although only three papers included specific analysis relating to the impact of volunteers. The evidence suggests volunteers may have potential to enhance the experiences of people with dementia in acute hospitals; however, there is currently a marked lack of evidence to support the widespread implementation of volunteers. There is therefore an urgent need for multi-site robust research to provide evidence of the impact of volunteers supporting people with cognitive impairment/dementia during an acute hospital stay.