BACKGROUND: Infective endocarditis (IE) with involvement of the aortic root is associated with high short-term mortality and morbidity. Long-term data are sparse, and the existing studies with long-term data are restricted by a low number of patients and do not report mortality risks of different age groups. OBJECTIVE: This study examined the all-cause mortality risk postoperatively of patients with first-time IE who underwent aortic root replacement (ARR), according to age at the time of surgery, with one and 10 years follow-up. METHODS: Patients with first-time IE who underwent ARR surgery from 2000-2016 were identified in Danish nationwide administrative registries and divided into age groups: ≤60, 61-74, and ≥75 years. We compared one- and 10-year mortality risk using multivariable Cox regression across the three age groups. RESULTS: We identified 258 patients who underwent ARR (26.0% female, 42.6% with prosthetic valves, median age 64 years (IQR 55-73), of whom 98, 112, and 48 patients were ≤60 years, 61-74 years, and >75 years, respectively. The corresponding in-hospital mortality risk was 10.2%, 22.3%, and 29.2% (P = .01), respectively. The one-year postoperative mortality risk was 17.3%, 28.6%, and 33.3% (P = 0.05), while at 10 years after surgery, it was 31.8%, 62.9%, and 77.1% (P < 0.01), respectively. The adjusted 10-year hazard ratio was higher in the 61-74 and >75-year age groups (HR 1.94 [1.18-3.16] and 2.46 [1.35-4.49]) compared with the ≤60. CONCLUSION: Aortic root replacement in patients with first-time IE was associated with a high in-hospital and one- and 10-year mortality with worse outcomes with age.