Background We aimed to identify the clinical and echocardiographic determinants of symptoms and their prognostic implications in patients with moderately dysfunctional bicuspid aortic valves (BAVs). Methods Among 1,019 subjects in the BAV registry treated in a single tertiary care center, the records of 127 patients (85 men, age 58±13 years) with moderately dysfunctional BAVs were comprehensively reviewed. The patients were divided into two groups based on symptom status: asymptomatic (n = 80) vs. symptomatic (n = 47). The primary end-point was defined as a composite of aortic valve surgery, hospitalization for heart failure, and any cause of death. Results The symptomatic group had a higher proportion of females, hypertension, aortic stenosis, and aortopathy than did the asymptomatic group. The symptomatic group showed lower e0 (5.5±1.7 vs. 6.5±2.2 cm/s, p = 0.003), higher E/e0 (13.3 ± 4.9 vs. 10.9±3.7, p = 0.002), and larger left atrial volume index (29.9±11.4 vs. 24.6±9.1 ml/m2 , p = 0.006) than did the asymptomatic group. In multivariate logistic regression analysis, female gender (odds ratio [OR] 2.84, 95% confidence interval [CI] 1.10-7.36, p = 0.031), hypertension (OR 3.07, 95% CI 1.20-7.82, p = 0.019), moderate aortic stenosis (OR 5.33 5.78, 95% CI 1.99-16.83, p = 0.001), E/e0 >15 (OR 3.82, 95% CI 1.03-11.19, p = 0.015), and aortopathy (OR 2.76, 95% CI 1.07-7.10, p = 0.035) were independently correlated with symptom status. The symptomatic group showed a significantly lower rate of event-free survival during the 8-year follow-up period (54±9% vs. 68±10%, p = 0.001).Conclusions In patients with moderately dysfunctional BAVs, the presence of moderate aortic stenosis, aortopathy, and diastolic dysfunction determines symptom status, along with female gender and hypertension. Symptom status was associated with clinical outcomes.