Objectives Few studies describe the trajectories of cognitive function for hip‐fracture patients following hospital discharge and the treatment effects of interdisciplinary intervention on cognitive outcomes. The purpose of this study was to explore the 2‐year postoperative trajectory for cognitive function of older hip‐fracture patients and cognitive effects of an interdisciplinary intervention. Methods Of 160 subjects randomly assigned to groups, 29 (35.8%) in the control group (n = 81) and 30 (38.0%) in the intervention group (n = 79) were cognitively impaired at admission. The intervention group received geriatric consultation, continuous rehabilitation, and discharge planning. Subjects' cognitive function was measured using the mini mental state examination Taiwan version at admission, 6, 12, 18, and 24 months after discharge and analyzed using hierarchical generalized linear models. Results Patients who received the intervention program had 75% less likelihood of being cognitively impaired 6 months following discharge than those who received routine care (odds ratio = 0.25, p < 0.001). The difference between the control and intervention groups was small at admission, peaked at 18 months, and decreased from 18 to 24 months following discharge. Conclusions Our interdisciplinary intervention improved the long‐term postoperative cognitive functioning of older persons with hip fracture in Taiwan. Copyright © 2013 John Wiley & Sons, Ltd.