Objective To estimate a safe minimum hospital volume for hospitals performing coronary artery bypass graft (CABG) surgery. Data Source Hospital data on all publicly funded CABG in five European countries, 2007–2009 (106,149 patients). Design Hierarchical logistic regression models to estimate the relationship between hospital volume and mortality, allowing for case mix. Segmented regression analysis to estimate a threshold. Findings The 30‐day in‐hospital mortality rate was 3.0 percent overall, 5.2 percent (95 percent CI: 4.0–6.4) in low‐volume hospitals, and 2.1 percent (95 percent CI: 1.8–2.3) in high‐volume hospitals. There is a significant curvilinear relationship between volume and mortality, flatter above 415 cases per hospital per year. Conclusions There is a clear relationship between hospital CABG volume and mortality in Europe, implying a “safe” threshold volume of 415 cases per year.