BACKGROUND: Comprehensive Geriatric Assessment (CGA) is now the accepted gold standard for caring for frail older people in hospital. However, there is uncertainty about identifying and targeting suitable recipients and which patients benefit the most. OBJECTIVES: our objectives were to describe the key elements, principal measures of outcome and the characteristics of the main beneficiaries of inpatient CGA. METHODS: we used the Joanna Briggs Institute umbrella review method. We searched for systematic reviews and meta-analyses describing CGA services for hospital inpatients in the Cochrane Database of Systematic Reviews, Database of Reviews of Effectiveness (DARE), MEDLINE and EMBASE and a range of other sources. RESULTS: we screened 1,010 titles and evaluated 419 abstracts for eligibility, 143 full articles for relevance and included 24 in a final quality and relevance check. Thirteen reviews, reported in 15 papers, were selected for review. The most widely used definition of CGA was: 'a multidimensional, multidisciplinary process which identifies medical, social and functional needs, and the development of an integrated/co-ordinated care plan to meet those needs'. Key clinical outcomes included mortality, activities of daily living and dependency. The main beneficiaries were people ≥55 years in receipt of acute care. Frailty in CGA recipients and patient related outcomes were not usually reported. CONCLUSIONS: we confirm a widely used definition of CGA. Key outcomes are death, disability and institutionalisation. The main beneficiaries in hospital are older people with acute illness. The presence of frailty has not been widely examined as a determinant of CGA outcome.