Background: Treatment of moderate functional mitral regurgitation (FMR) during aortic valve replacement (AVR) is controversial. This study aimed to evaluate the effect of different surgical strategies in patients with moderate FMR undergoing AVR. Methods: A total of 468 patients with moderate FMR undergoing AVR from January 2010 to December 2019 were retrospectively studied comparing 3 different surgical strategies, namely isolated AVR, AVR + mitral valve repair (MVr) and AVR + mitral valve replacement (MVR). Survival was estimated using the Kaplan-Meier method and compared with the log-rank test, followed by inverse probability treatment weighting (IPTW) analysis to adjust the between-group imbalances. The primary outcome was overall mortality. Results: Patients underwent isolated AVR (35.3%), AVR + MVr (30.3%), or AVR + MVR (34.4%). The median follow-up was 27.1 months. AVR + MVR was associated with better improvement of FMR during the early and follow-up period compared to isolated AVR and AVR + MVr (p 0.001). Compared to isolated AVR, AVR + MVR increased the risk of mid-term mortality (hazard ratio [HR]: 2.13, 95% confidence interval [CI]: 1.01–4.48, p = 0.046), which was sustained in the IPTW analysis (HR: 4.15, 95% CI: 1.69–10.15, p = 0.002). In contrast, AVR + MVr showed only a tendency to increase the risk of follow-up mortality (HR: 1.63, 95% CI: 0.72–3.67, p = 0.239), which was more apparent in the IPTW analysis (HR: 2.54, 95% CI: 0.98–6.56, p = 0.054). Conclusions: In patients with severe aortic valve disease and moderate FMR, isolated AVR might be more reasonable than AVR + MVr or AVR + MVR.