Background: Although the intra-septal method offers better access to the mitral valve, there are concerns over the increased likelihood of postoperative atrial fibrillation and full heart block. Aim: To compare incidence of postoperative arrhythmia between bi-atrial trans-septal approach and left atrial approach in mitral valve surgery, to improve outcome and quality of life to reduce morbidity and mortality. Patients and methods: This comparative prospective clinical trial was done in Cardio-Thoracic Surgery Department and Clinic in Faculty of Medicine in Suez Canal University Hospital for Health Insurance and Ismailia Medical Complex. This study included 100 participants who were separated into 2 groups: group A: 50 patients who were going to have trans-septal approach and group B: 50 patients who were going to have left atriotomy. Results: Operative details of the studied groups found that the mean cross-clamp time in trans-septal group was statistically significantly higher than in left atriotomy group (p=0.020). The mean CPB time in trans-septal group was statistically significantly higher than in left atriotomy group (p=0.022). Postoperative assessment of the studied groups found that the mean EF in trans-septal group was statistically significantly higher than in left atriotomy group (p=0.015). Conclusion: The findings of our trial demonstrate that compared to left atriotomy, the TS approach was linked to longer pump as well as cross-clamp times, as well as an increased risk of postoperative atrial fibrillation, pleural effusion, postoperative mean EF, and mean duration of inotropic use.