Long and mid-term data in Low-Flow Low-Gradient Aortic Stenosis (LFLG-AS) are scarce. The present study sought to identify predictors of outcome in a sizeable cohort of patients with LFLG-AS. 76 consecutive patients with LFLG-AS (defined by a mean gradient <40 mmHg, an aortic valve area ≤1 cm2 and an ejection fraction ≤50%) were prospectively enrolled and followed at regular intervals. Events defined as aortic valve replacement (AVR) and death were assessed and overall survival was determined. 44 patients underwent AVR (10 transcatheter and 34 surgical) whilst intervention was not performed in 32 patients, including 9 patients that died during a median waiting time of 4 months. Survival was significantly better after AVR with survival rates of 91.8% (CI 71.1–97.9%), 83.0% (CI 60.7–93.3%) and 56.3% (CI 32.1–74.8%) at 1,2 and 5 years as compared to 84.3% (CI 66.2–93.1%), 52.9% (CI 33.7–69.0%) and 30.3% (CI 14.6–47.5%), respectively, for patients managed conservatively (p = 0.017). The presence of right ventricular dysfunction (HR 3.47 [1.70–7.09]) and significant tricuspid regurgitation (TR) (HR 2.23 [1.13–4.39]) independently predicted overall mortality while the presence of significant TR (HR 3.40[1.38–8.35]) and higher aortic jet velocity (HR 0.91[0.82–1.00]) were independent predictors of mortality and survival after AVR. AVR is associated with improved long-term survival in patients with LFLG-AS. Treatment delays are associated with excessive mortality, warranting urgent treatment in eligible patients. Right ventricular involvement characterized by the presence of TR and/or right ventricular dysfunction, identifies patients at high risk of mortality under both conservative management and after AVR.