Background: Surgical ablation (SA) for atrial fibrillation (AF) concomitant to mitral valve repair/replacement (MVRR) improves longitudinal sinus rhythm. However, the risk of adding SA remains a clinical question. This study examined whether the addition of contemporary SA for AF has an impact on operative outcomes. Methods: The study cohort included 88,765 MVRR patients with or without SA, coronary artery bypass grafting (CABG), septal defect, and tricuspid repair in The Society of Thoracic Surgeons Database between 2011 and 2014. Group 1 did not have AF (No-AF) and did not receive SA (No-SA); group 2 had No-AF immediately preoperatively but received SA; group 3 had AF but No-SA; and group 4 had AF with SA. Groups 3 and 4 were stratified into paroxysmal versus nonparoxysmal AF. With the use of logistic regression, with group 1 as reference, risk-adjusted odds ratios (OR) for mortality were compared for SA performance, AF type, and SA technique. Results: Group 3 had higher age, New York Heart Association class, redo operations, and unadjusted mortality than group 4. Relative to group 1, group 3 had an OR for mortality of 1.15 (95% confidence interval: 1.04 to 1.27, p < 0.01). OR increments were similar for paroxysmal and nonparoxysmal AF. In group 4, concomitant SA was independently associated with lower AF-related relative risk (OR 1.08), to a level that was not different from group 1 (p = 0.13). Observed treatment effects were equivalent for paroxysmal and nonparoxysmal AF and across all levels of baseline risk. Conclusions: For patients with AF at the time of mitral operation, the performance of SA seems associated with a lower risk-adjusted operative mortality compared with patients who do not undergo ablation.