This randomized clinical trial aimed to determine whether preoperative cognitive training reduces the incidence of delirium in patients undergoing coronary artery bypass grafting (CABG). The study was conducted at three university teaching hospitals in southeastern China from April 2022 to May 2023. Eligible participants were those scheduled for elective CABG who consented and enrolled at least 10 days before surgery. Patients were randomly assigned 1:1 to either routine care or cognitive training, which included substantial practice on online tasks designed to enhance cognitive functions such as memory, imagination, reasoning, reaction time, attention, and processing speed. The primary outcome was the occurrence of delirium during postoperative days 1 to 7 or until hospital discharge, diagnosed using the Confusion Assessment Method or the Confusion Assessment Method for Intensive Care Units. Secondary outcomes included postoperative cognitive dysfunction, delirium characteristics, and all-cause mortality within 30 days following the operation. A total of 218 patients were randomized, with 208 included in the final analysis. The cognitive training group had a lower incidence of delirium (27.5%) compared to the routine care group (43.4%), with an adjusted odds ratio (aOR) of 0.43 (95% CI, 0.23-0.77; P = .007). Significant differences were also observed in the incidence of severe delirium, median duration of delirium, and median number of delirium-positive days. The study concluded that preoperative cognitive training may reduce the incidence of delirium in patients recovering from CABG surgery, but the primary analysis was based on fewer than 75 events, making it exploratory and a basis for future larger trials.This randomized clinical trial aimed to determine whether preoperative cognitive training reduces the incidence of delirium in patients undergoing coronary artery bypass grafting (CABG). The study was conducted at three university teaching hospitals in southeastern China from April 2022 to May 2023. Eligible participants were those scheduled for elective CABG who consented and enrolled at least 10 days before surgery. Patients were randomly assigned 1:1 to either routine care or cognitive training, which included substantial practice on online tasks designed to enhance cognitive functions such as memory, imagination, reasoning, reaction time, attention, and processing speed. The primary outcome was the occurrence of delirium during postoperative days 1 to 7 or until hospital discharge, diagnosed using the Confusion Assessment Method or the Confusion Assessment Method for Intensive Care Units. Secondary outcomes included postoperative cognitive dysfunction, delirium characteristics, and all-cause mortality within 30 days following the operation. A total of 218 patients were randomized, with 208 included in the final analysis. The cognitive training group had a lower incidence of delirium (27.5%) compared to the routine care group (43.4%), with an adjusted odds ratio (aOR) of 0.43 (95% CI, 0.23-0.77; P = .007). Significant differences were also observed in the incidence of severe delirium, median duration of delirium, and median number of delirium-positive days. The study concluded that preoperative cognitive training may reduce the incidence of delirium in patients recovering from CABG surgery, but the primary analysis was based on fewer than 75 events, making it exploratory and a basis for future larger trials.