Objective To explore the risk factors for new-onset atrial fibrillation (POAF) after off-pump coronary artery bypass grafting (OPCAB) alone. Methods A retrospective analysis was conducted on the clinical data of patients who underwent OPCAB in the Department of Cardiac Surgery Ward No.1 of Zhengzhou Seventh People’s Hospital from January 2020 to January 2024. Patients were categorized into POAF and non-POAF groups based on the occurrence of POAF. The clinical data of both groups were analyzed. Parameters underwent single-factor analysis, and variables with P≤0.05 in single-factor analysis were further analyzed through binary logistic regression to identify independent risk factors. Results A total of 496 patients were included. There were 312 males and 184 females, with age ranging from 50 to 78 years. There were 148 patients in the POAF group and 348 patients in the non-POAF group. The incidence of POAF after isolated OPCAB surgery was 29.8%. Results of univariate analysis showed that there was statistical difference in the incidence of diabetes (P=0.012), >75% stenosis of the left circumflex artery (LCX) (P=0.036), shock (P<0.001), graded left ventricular diastolic function (P<0.001), left ventricular ejection fraction (P<0.001), age (P<0.001), preoperative resting heart rate (P<0.001), left atrial diameter (P<0.001), E/A ratio (P<0.001), postoperative K+ concentration (P<0.001), and postoperative Mg2+ concentration (P<0.001). Binary logistic regression multifactor analysis revealed that age (OR=1.436, 95%CI 1.094 to 1.884, P=0.009), diabetes (OR=2.032, 95%CI 1.094 to 1.884, P=0.043), preoperative resting heart rate (OR=1.008, 95%CI 1.001 to 0.018, P=0.018), left atrial diameter (OR=4.409, 95%CI 1.711 to 11.359, P=0.002), E/A ratio (OR=1.713, 95%CI 1.115 to 2.633, P=0.014). The occurrence of POAF significantly prolonged mechanical ventilation time and ICU stay (both P＜0.001). Conclusion Age, diabetes, left atrial diameter, EA ratio, and preoperative resting heart rate are potential independent risk factors for POAF following OPCAB surgery. Additionally, the occurrence of POAF post-surgery can lead to prolonged mechanical ventilation and extended stay in the intensive care unit.