Tricuspid valve repair for mild tricuspid regurgitation during rheumatic mitral valve surgery is controversial. We evaluated the benefit of tricuspid valve repair for mild tricuspid regurgitation in rheumatic mitral valve surgery.Among 1208 consecutive patients (52.6 ± 11.9 years) with mild tricuspid regurgitation who underwent rheumatic mitral valve surgery from 2000 to 2018 in 2 referral centers, 419 received concomitant tricuspid valve repair and 789 did not. The primary end point was the development of severe tricuspid regurgitation. Deaths were regarded as competing events. Secondary end points were death and heart failure. Inverse probability of treatment weighting was performed to reduce selection bias. Multivariable competing risk analysis was performed to determine the predictive factors of severe tricuspid regurgitation.There was no significant difference in early mortality rates between patients with and without tricuspid valve repair (P = .26). During a median follow-up of 71.6 (interquartile range: 25.3-124.2) months, the primary end point was detected in 7 of 419 patients (0.25%/patient-years) and 28 of 789 patients (0.57%/patient-years) with and without tricuspid valve repair, respectively (P = .04). There were no significant differences in the secondary end points. After baseline adjustment, the primary end point was not significantly different depending on the addition of tricuspid valve repair (hazard ratio, 0.64; 95% confidence interval, 0.23-1.77; P = .39). In multivariable analysis, only the omission of surgical atrial fibrillation ablation (hazard ratio, 4.52; 95% confidence interval, 2.07-9.87) was significantly associated with the development of severe tricuspid regurgitation.Tricuspid valve repair for mild tricuspid regurgitation in rheumatic mitral valve surgery provides no overt clinical benefit.