Introduction. Dementia is a group of different progressive diseases that currently has no cure. In diseases with limited disease modifying therapy, success of treatment is often measured by improving the QOL of the individual. Dementia causes a decrease in cognitive function, so QOL has historically been reported by proxies such as family members or health-care providers. The aim was to conduct a systematic review of the literature to determine how QOL was assessed in adults, 65 years and older with dementia, and identify factors that influence the reported scores. Methods. A systematic review of full-text articles addressing QOL in older adults with dementia, published in English from January 2000 to September 2020, was conducted using PubMed and PsycINFO. We included studies that assessed QOL and involved participants 65 years and older. Studies were evaluated for inclusion by 2 independent pairs of reviewers. Study characteristics and findings were summarized. We identified social and clinical factors influencing QOL scores. Results. 19 of the 928 articles found met the requirements for inclusion. These 19 studies, with sample sizes ranging from 32 to 1,366, included 6,279 dementia patients. The participants’ average age ranged from 77.1 to 86.6 years. Five measuring tools were identified: DEMQOL (health-related QOL for people with dementia), QUALIDEM (a dementia-specific QOL instrument), Quality of Life in Late-Stage Dementia (QUALID), and Quality of Life in Alzheimer Disease (QOL-AD). In terms of QOL, self-ratings were superior to proxy ratings. Depression, functional impairment, and polypharmacy were among the factors that frequently affected how well people rated their own quality of life. Functional impairment, the prevalence of neuropsychiatric symptoms, cognitive impairment, and caregiver strain were frequently found to have an impact on proxy assessments. Conclusion. Self- and proxy reports may work together to evaluate QOL in dementia and make sure that all viewpoints are taken into account.