Objective: To identify functional performance trajectories and the characteristics of people who receive inpatient geriatric rehabilitation after hospital admissions. Design, setting, participants: REStORing health of acutely unwell adulTs (RESORT) is an observational, prospective, longitudinal inception cohort study of consecutive patients admitted to geriatric rehabilitation wards at the Royal Melbourne Hospital. Recruitment commenced on 15 October 2017. Main outcome measures: Functional performance, assessed with the Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) scales two weeks before acute hospitalisation, on admission to and discharge from geriatric rehabilitation, and three months after discharge from geriatric rehabilitation. Results: A total of 618 rehabilitation patients were included in our analysis. For each of the two scales, three distinct functional performance trajectories were identified by latent class growth modelling: poor at baseline and 3-month follow-up (remained poor: ADL, 6.6% of patients; IADL, 42%), good at baseline but poor recovery (deteriorated: ADL, 33%; IADL, 20%), and good at baseline and good recovery (recovered: ADL, 60%; IADL, 35%). Higher Clinical Frailty Scale (CFS) score (v recovered, per point: odds ratio [OR], 2.51; 95% CI, 1.64–3.84) and cognitive impairment (OR, 6.33; 95% CI, 2.09–19.1) were associated with greater likelihood of remaining poor in ADL, and also with deterioration (CFS score: OR, 1.76; 95% CI, 1.45–2.13; cognitive impairment: OR, 1.87; 95% CI, 1.24–2.82). Higher CFS score (OR, 1.64; 95% CI, 1.37–1.97) and cognitive impairment (OR, 3.60; 95% CI, 2.31–5.61) were associated with remaining poor in IADL, and higher CFS score was also associated with deterioration (OR, 1.63; 95% CI, 1.33–1.99). Conclusions: Based on ADL assessments, most people who underwent inpatient geriatric rehabilitation regained their baseline functional performance. As higher CFS score and cognitive impairment were associated with poorer functional recovery, assessing frailty and cognition at hospital admission could assist intervention and discharge planning.