Abstract Purpose To describe the clinical features of COVID-19 in older adults, and relate these to outcomes. Methods A cohort study of 217 individuals (median age 80, IQR 74–85 years; 62% men) hospitalised with COVID-19, followed up for all-cause mortality, was conducted. Secondary outcomes included cognitive and physical function at discharge. C-reactive protein and neutrophil:lymphocyte ratio were used as measures of immune activity. Results Cardinal COVID-19 symptoms (fever, dyspnoea, cough) were common but not universal. Inflammation on hospitalisation was lower in frail older adults. Fever, dyspnoea, delirium and inflammation were associated with mortality. Delirium at presentation was an independent risk factor for cognitive decline at discharge. Conclusions COVID-19 may present without cardinal symptoms as well as implicate a possible role for age-related changes in immunity in mediating the relationship between frailty and mortality.