Isolated tricuspid valve surgery (ITVS) is reputed to be a high-risk surgery, but in-hospital mortality is markedly variable. This study sought to develop a dedicated risk score model to predict the outcome of patients after ITVS for severe tricuspid regurgitation (TR). All consecutive adult patients who underwent an ITVS for severe TR at 12 French centers between 2007 and 2017 were included. We derived and internally validated a scoring system to predict in-hospital mortality using multivariable logistic regression and bootstrapping with 1000 re-samples. We identified 466 patients (60 ± 16 years, 49% female, functional TR in 49%). In-hospital mortality rate was 10%. The final risk score ranged from 0 to 12 points and included 8 parameters: age ≥ 70 years, New-York Heart Association class III-IV, right-sided heart failure signs, daily dose of furosemide ≥ 125 mg, glomerular filtration rate < 30 ml/min, elevated bilirubin, left-ventricular ejection fraction < 60% and moderate/severe right-ventricular dysfunction. TR mechanism was not an independent predictor of outcome. Observed and predicted in-hospital mortality rates increased from 0% to 60% and from 1% to 65% respectively as score increased from 0 up to ≥ 9 points. Apparent and bias-corrected areas under the receiver operating characteristic curves were 0.81 and 0.75 respectively, much higher than the logistic EuroSCORE (0.67) or EuroSCORE II (0.63). We proposed an accurate dedicated risk-score model based on eight easy to ascertain parameters to inform patients and physicians regarding the risk of ITVS and guide the clinical decision-making process of patients with severe TR, especially as transcatheter therapies are emerging.