The purpose of this research was to investigate risk factors of comorbidity, inflammatory response, postoperative pain, and postoperative delirium for postoperative cognitive dysfunction (POCD) in older adults undergoing coronary artery bypass grafting. The sample consisted of 120 older adults who had coronary artery bypass grafting. Data were collected by using the Mini-Mental State Examination (MMSE-Thai 2000), the Charlson Comorbidity Index (CCI), the Systemic Inflammatory Response Syndrome (SIRS) scale, the Postoperative Pain scale and the Thai version of the Confusion Assessment Method (CAM). Data analysis was done using chi-square and logistic regression. The results revealed that 49.20 percent of the sparticipants had postoperative cognitive dysfunction. Logistic regression analysis showed that inflammatory response, postoperative pain, and postoperative delirium together predicted with 35.7 percent of the variation in postoperative cognitive dysfunction (Nagelkerke: R2=.357, p<.05) but comorbidity was not significant for predicting postoperative cognitive dysfunction. Therefore, the factors associated with postoperative cognitive dysfunction should be further studied. However, these research findings can be developed for surveillance and care plans so as to prevent the incidence of postoperative cognitive dysfunction.