BACKGROUND: There is limited understanding of the contribution made by older people and their caregivers to acute healthcare in the home and how this compares to hospital inpatient healthcare. OBJECTIVES: To explore the work of older people and caregivers at the time of an acute health event, the interface with professionals in a hospital and hospital at home (HAH) and how their experiences relate to the principles underpinning comprehensive geriatric assessment (CGA). DESIGN: A qualitative interview study within a UK multi-site participant randomised trial of geriatrician-led admission avoidance HAH, compared with hospital inpatient care. METHODS: We conducted semi-structured interviews with 34 older people (15 had received HAH and 19 hospital care) alone or alongside caregivers (29 caregivers; 12 HAH, 17 hospital care), in three sites that recruited participants to a randomised trial, during 2017-2018. We used normalisation process theory to guide our analysis and interpretation of the data. RESULTS: Patients and caregivers described efforts to understand changes in health, interpret assessments and mitigate a lack of involvement in decisions. Practical work included managing risks, mobilising resources to meet health-related needs, and integrating the acute episode into longer-term strategies. Personal, relational and environmental factors facilitated or challenged adaptive capacity and ability to manage. CONCLUSIONS: Patients and caregivers contributed to acute healthcare in both locations, often in parallel to healthcare providers. Our findings highlight an opportunity for CGA-guided services at the interface of acute and chronic condition management to facilitate personal, social and service strategies extending beyond an acute episode of healthcare.