Delirium is a transient neurocognitive disorder. Nonpharmacological measures can be efficient in reducing the incidence and intensity of delirium, but there is a paucity of evidence when using a physical exercise program exclusively. This was a secondary analysis of a randomised clinical trial that provided evidence on the functional and cognitive benefits of an individualised exercise intervention in hospitalised older adults. Of the 370 patients who participated in the trial, 17.1% in the intervention group had delirium and 12.1% in the control group. After the exercise intervention, 84.6% of the patients in the intervention group showed improvement in delirium compared to 68.4% of patients in the control group. Despite the fluctuating nature of delirium, we show that it is feasible to establish individualised exercise interventions in hospitalised geriatric patients in the periods when patients are able to cooperate. Baseline functional status, measured by the Barthel Index, is a clinical marker that could help to identify those who will benefit most.