Postoperative delirium (POD) is a common and serious neuropsychiatric syndrome that leads to higher morbidity and mortality. We investigated the association between serum C-reactive protein (CRP) and the occurrence of POD in older hip fracture patients, and whether CRP predicted POD better than a clinical model. Patients aged ≥ 75years admitted for surgical repair of an acute hip fracture were recruited. We compared serum CRP levels between patients with and without POD. Sixty patients were included, of whom 21 (35%) developed POD. Serum CRP levels were significantly higher in patients who developed delirium (p = 0.011). In a multiple regression model including clinical variables and CRP, cognitive impairment (p = 0.003) and infection (p = 0.001) were the best predictors of POD. Although higher levels of serum CRP were significantly associated with POD in older hip fracture patients, pre-existing cognitive impairment and infections were the most important risk factors for POD.