The Frazier Free Water Protocol was developed with the aim of providing patients with dysphagia an option to consume thin (i.e. unthickened) water in-between mealtimes. A systematic review was conducted of research published in peer-reviewed journals. An electronic search of the EMBASE, CINAHL and MEDLINE databases was completed up to July 2016. A total of 8 studies were identified for inclusion: 5 randomised controlled trials, 2 cohort studies with matched cases and 1 single group pre-post intervention prospective study. A total of 215 rehabilitation inpatients and 30 acute patients with oropharyngeal dysphagia who required thickened fluids or were to remain 'nil by mouth', as determined by bedside swallow assessment and/or videofluoroscopy/fiberoptic endoscopic evaluation of swallowing, were included. Meta-analyses of the data from the rehabilitation studies revealed (1) low-quality evidence that implementing the protocol did not result in increased odds of having lung complications and (2) low-quality evidence that fluid intake may increase. Patients' perceptions of swallow-related quality of life appeared to improve. This review has found that when the protocol is closely adhered to and patients are carefully selected using strict exclusion criteria, including an evaluation of their cognition and mobility, adult rehabilitation inpatients with dysphagia to thin fluids can be offered the choice of implementing the Free Water Protocol. Further research is required to determine if the Free Water Protocol can be implemented in settings other than inpatient rehabilitation.