BACKGROUND: This study aims to determine whether tricuspid regurgitation (TR) ≥ 2+ requires attention during mitral valve surgery. METHODS: From April 1999 to 2009, 161 patients undergoing primary, isolated mitral valve procedures were assessed. Preoperative moderate TR (≥2+) was present in 56 of 161 patients and tricuspid valve repair (TVR: ring annuloplasty) was carried out on 22 of 56 patients with TR ≥ 2+. Baseline echocardiogram included TR severity (ASE criteria), TR velocity, estimated right atrial pressure, visual assessment of right ventricular failure and strain. Follow-up was 47 ± 33 months (96% complete); 91 of 161 patients overall (57%) and 44 of 45 patients with TR ≥ 2+ had follow-up echocardiogram. RESULTS: Patients with moderate TR had worse baseline functional class and operative risks, both worst in the non-TVR group. Overall mortality was 15% (n = 23), comprising 2.5% (4/161) 30-day mortality and 12% (9/157) late death. Poorer preoperative TR was associated with worse survival by univariate analysis (P = 0.046), after correction for right ventricular function and pulmonary artery pressure (P = 0.049), age and diabetes (P = 0.041). Despite lower risk of TR ≥ 2+ with TVR, 5-year survival was 42%, which was less than TR < 2+ and that of non-TVR group (90%, P = 0.003). Improvement in overall functional class (NYHA) was better in the non-TVR group (TVR: preoperative 2.1 ± 1.5; post-operative 1.2 ± 1.1 (P = 0.02) versus non-TVR: preoperative 1.8 ± 1.4, post-operative 1.2 ± 0.9 (P < 0.0001)). There was no difference in quality of life (QOL) indices (SF-36 questionnaire) at follow-up between patients with TR < 2+ and TR ≥ 2+ preoperatively, or across all levels of TR before or after surgical repair. CONCLUSIONS: Preoperative TR ≥ 2+, non-TVR group had more favourable functional class and mid-term survival with comparable QOL and echocardiographic parameters to the TVR group.