This study sought to assess the long-term outcome of active surveillance in these patients. The optimal timing of mitral valve surgery in asymptomatic primary mitral regurgitation (MR) remains controversial. Between 1997 and 2015, 280 consecutive patients with severe asymptomatic primary MR were enrolled in our heart valve clinic follow-up program. They were prospectively followed up every 6 months clinical and echocardiographical examinations until surgical criteria were reached. Event-free survival and overall survival as compared with the age- and gender-matched general population were assessed. During a median potential follow-up of 93.4 (quartiles 55.3 to 152.9) months, 161 patients developed an indication for surgery and 13 patients died. Event-free survival rates were 78.0% (95% confidence interval CI: 73.2% to 83.2%) at 2 years, 52.2% (95% CI: 46.3% to 59.0%) at 6 years, 35.5% (95% CI: 29.3% to 43.1%) at 10 years, and 18.7% (95% CI: 12.3% to 28.5%) at 15 years. Overall survival rate was 99.6% (95% CI: 98.9% to 100%) at 2 years, 94.6% (95% CI: 91.7% to 97.6%) at 6 years, 85.6% (95% CI: 80.3% to 91.2%) at 10 years, and 74.5% (95% CI: 66.6% to 83.4%) at 15 years. Overall survival of patients managed according to an active surveillance strategy was comparable with the expected cumulative survival and early survival rates were even better in the study population (standardized mortality ratio: 0.667; 95% CI: 0.463 to 0.963; p = 0.013). Patients with severe asymptomatic primary MR may remain free of indications for surgery for extensive periods of time. In such patients, active surveillance performed in experienced centers is associated with a favorable prognosis, resulting in timely referral to surgery, excellent long-term survival, and good surgical outcomes. Display omitted