The capacity to make reasoned decisions about one’s health care is central to optimal person-centered care. Termed ‘decision-making capacity’, it requires comprehension of the information presented about one’s health, an understanding of one’s circumstances and the reasoning skills to navigate health care options. Impaired decision-making capacity is prevalent in hospital settings whilst also being under-recognized leading to sub-optimal care and raising ethical concerns. This assesses decision-making capacity all the more important in this setting. This scoping review aimed to explore and summarise the literature on current practice in the assessment of decision-making capacity in hospital settings. A total of four databases (Psychinfo, CINAHL, Scopus and Medline) were searched from 2009 to June 2019, using search terms related to ‘assessment’, ‘decision-making capacity’ and ‘patient’. Thirteen studies were included. They investigated a variety of methods for assessing decision-making capacity in hospital settings. No gold standard test emerged. Commonly, it was doctors that assessed decision-making capacity with an informal interview with the patient; however, the error rate for this assessment was up to 58%. The literature suggests that training in this method and/or the use of more structured assessment tools may be required to improve the accuracy of decision-making capacity assessment. Another finding was that decision-making capacity assessments rely heavily on patient communication abilities. Therefore, all efforts should be made to provide communication assistance, for support with patients who have complex communication needs (including engagement with Speech and Language Pathology services). Finally, healthcare services must ensure health professionals performing capacity assessments receive appropriate training and that robust policy are in place to support improved assessment practices.