Abstract Purpose Surgery is required in 20–50% of patients with infective endocarditis (IE). Frailty increases surgical risk; however, the prognostic implications of frailty in patients undergoing IE-related surgery remain poorly understood. We aimed to assess the association between frailty and all-cause mortality or rehospitalization after discharge (≥ 14 days). Methods We identified all IE patients who underwent surgery during admission (2010–2020) in Denmark. The Hospital Frailty Risk Score was used to categorize patients into two frailty risk groups, patients with low frailty scores (< 5 points) and frail patients (≥ 5 points). We analyzed time hospitalized after discharge and all-cause mortality from the date of surgery with a one-year follow-up. Statistical analyses utilized the Kaplan–Meier estimator, Aalen–Johansen estimator, and the Cox regression model. Results We identified 1282 patients who underwent surgery during admission, of whom 967 (75.4%) had low frailty scores, and 315 (24.6%) were frail. Frail patients were characterized by advanced age, a lower proportion of males, and a higher burden of comorbidities. Frail patients were more hospitalized (> 14 days) in the first post-discharge year (19.1% vs.12.3%) compared to patients with low frailty scores. Additionally, frail patients had higher rates of all-cause mortality including in-hospital deaths (27% vs. 15%) and rehospitalizations (43.5% vs 26.1%) compared to patients with low frailty scores. This was also evident in the adjusted analysis (hazard ratio 1.36 [CI 95% 1.09–1.71]). Conclusion Frailty was associated with an ≈40% increased rate of rehospitalization (≥ 14 days) or death. Further studies are needed to assess the effectiveness of surgery with a focus on frailty to improve prognostic outcomes in these patients.