Background: Postoperative cognitive dysfunction (POCD) is commonly observed following cardiac surgery. The utilization of cardiopulmonary bypass (CPB) is associated with many possible mechanisms to cause POCD. However, there is no evidence confirming that CPB alone is the cause of POCD. Objectives: The current study aimed at evaluating several factors suspected to cause POCD following cardiac surgery in Cipto Mangunkusumo Hospital, Jakarta, Indonesia. Methods: The current prospective cohort study was conducted on 54 patients who were candidates for cardiac surgery. The assessment of memory, attention, and executive functions was performed by neuropsychological tests, before and after the surgery. Cognitive decline was defined as a 20% decrease in cognitive function in at least one of the tests. Inclusion criteria were adults spokeing Bahasa Indonesia fluently, literate, and giving consent to participate in the study. The analyzed risk factors included age, diabetes, educational level, duration of aortic cross clamp, and duration of cardio-pulmonary bypass. Results: POCD occured in 40.7% of subjects that underwent cardiac surgery using cardiopulmonary bypass. Age was the only influential factor through bivariate test and logistic regression analysis (P = 0.001). The current study conducted a logistic regression test on age variable; the obtained result indicated an increasing trend of POCD in accordance with age group. Conclusions: Durations of CPB, cross clamp, diabetes, and educational level were not the main risks of POCD. Old age was a significant predictor to POCD. © 2018, Author(s).