The purpose of this study was to test a theoretical model to understand the influences of six predicting variables in post-surgical cognitive disturbance in older Taiwanese patients after elective surgery. The data were collected in a medical center in Taipei, Taiwan. Ninety-three patients were included in the final analysis. The findings showed that cognitive function at admission (beta=0.50, p<0.001), physical function at admission (beta=-0.34, p<0.001), and physiological stability (beta=-0.21, p<0.01) had direct effects on post-surgical cognitive disturbance. Physical function and cognitive function at admission also affected post-surgical cognitive disturbance indirectly through physiological stability. These variables accounted for 67% of the total variance of post-surgical cognitive disturbance. The findings from this study suggest that a careful and systematic assessment of the patient's condition at the time of admission is important. It is necessary to monitor and correct these variables at admission or before surgery to prevent or reduce the impact of post-operative delirium. It is also necessary to monitor these variables during the hospital stay to help nurses to distinguish the etiology of delirium. In each case, knowing when confusion is more likely to occur can assist in focusing more appropriate and effective efforts at detection, thereby reducing the consequences associated with confusion.