Background: Rocking chair therapy has been explored in patients with dementia to promote the feeling of relaxation, but not in Intensive Care Unit (ICU) patients with delirium. Aim: The aim is to investigate the effect of a chair with or without rocking motion on the duration of delirium and intensity of agitation in critically ill patients admitted to the ICU. Design: This is an investigator-initiated pragmatic, multicentre, parallel-grouped, centrally randomised, stratified, data analyst-blinded trial. Method: We will include patients for 1:1 web-based randomisation, stratified by site in patients 18 y or older with a positive delirium score identified by a validated tool. We will exclude patients mainly due to mobilisation restrictions, body weight exceeding 130 kg, inability to provide consent, and presence of multiresistant bacteria or viral droplet infections. The intervention group will receive a minimum of 20 min of rocking therapy daily. The control group will be transferred to the same type of chair but without rocking therapy daily. A power calculation with a risk reduction of 20%, a power of 80% with an alpha cut-off on 5% and further 20% inclusion gives 76 patients in intervention and control group reaching a total of n = 152 inclusion in the trial. Conclusion: The RockingICU trial will provide important new knowledge and raise research questions regarding nonpharmacological interventions to alleviate delirium in ICU patients.