BACKGROUND Postoperative delirium is common in patients undergoing coronary artery bypass grafting, characterized by cognitive decline. This study aimed to evaluate the effect of early planned mobilization on delirium after coronary artery bypass grafting. METHODS This double-blind randomized clinical trial enrolled 92 consecutive patients who underwent coronary artery bypass grafting from September to December 2018. The patients were divided into two groups of 46: a mobilization protocol was applied in the intervention group in the first 2 days after surgery; the control group received routine nursing care only. Demographic data, medical records, and Neecham confusion scores were analyzed. RESULTS Patients in the control group used cigarettes (31.1% vs. 11.1%, p = 0.020) and opium poppy for recreation (35.6% vs. 8.9%, p = 0.002) more frequently, had longer intubation times (11.91 ± 3.87 vs. 10.23 ± 2.71 h, p = 0.020), and fewer blood components infused (15.6% vs. 33.3%, p = 0.05). More patients in the intervention group had normal function on the 2nd postoperative day compared to the control group (25 vs. 2, respectively, p = 0.001). The intervention group had significantly higher Neecham scores on postoperative day 2 (22.49 ± 2.03 vs. 26.82 ± 2.10, p = 0.001). Multivariable analysis showed significant associations between Neecham score and age (p = 0.022), ejection fraction (p = 0.015), myocardial infarction (p = 0.016), systolic pressure (p = 0.009), and diastolic pressure (p = 0.008). CONCLUSIONS Early planned mobilization was effective in reducing postoperative delirium in patients undergoing coronary artery bypass grafting.