Abstract Background the number of older people living in residential and nursing care homes is rising. Loneliness is a major problem for older people, but little is known about the prevalence of loneliness amongst older people living in care homes. Aim to undertake a systematic review of literature on the prevalence of moderate and severe loneliness amongst older people living in residential and nursing care homes. Design we systematically reviewed the databases Cumulative Index to Nursing and Allied Health Literature (CINAHL), MEDLINE, PsycINFO, Embase, Scopus, Cochrane and Allied and Complementary Medicine Database (AMED) from inception to January 2019. We included all studies reporting data on the prevalence of loneliness amongst older people living in care homes. A random-effects meta-analysis was conducted on all eligible data. Results a total of 13 articles were included, representing 5,115 participants (age range of 55–102 years, mean age 83.5 years, 68% female). There was a significant variation between studies in estimates of prevalence. The prevalence of moderate loneliness ranged from 31 to 100%, and the prevalence of severe loneliness ranged from 9 to 81%. The estimated mean prevalence of ‘moderate loneliness’ was 61% (95% confidence interval (CI): 0.41, 0.80). The estimated mean prevalence of ‘severe loneliness’ was 35% (95% CI: 0.14, 0.60). Conclusion the prevalence of both moderate loneliness and severe loneliness amongst care home residents is high enough to warrant concern. However, the significant variation in prevalence estimates warrants further research. Future studies should identify which interventions can address loneliness and promote meaningful social engagement to enhance quality of life in care homes.