Despite many studies about aortic valve function and aortic root geometry after conservative aortic root repair of acute type A aortic dissection, the results are not always consistent or conclusive. This study aims to evaluate aortic root diameter and aortic valve function after surgery for acute type A aortic dissection involving the aortic root.A retrospective review was performed of 196 consecutive patients (age, 56.9 ± 11.4 years; 96 men) who underwent conservative aortic root repair including sinotubular junction resuspension for the management of acute type A aortic dissection involving the aortic root.The 30-day mortality rate was 5.1% (n = 10). During a median follow-up period of 45.3 ± 36.4 months, there were 28 deaths and 11 cases of aortic reoperation (proximal reoperation in 1 and distal reoperation in 10). Of the 6-month survivors (n = 177, 90.3%), echocardiography and computed tomography were performed in the late period (>6 months) on 115 (65.0%) and 138 (78.0%), respectively. Significant aortic regurgitation (greater than grade 2+) or root dilatation (>45 mm) was observed in 5 and 19 patients, respectively. Freedom from aortic regurgitation (greater than grade 2+) or root dilatation (>45 mm) at 5 years was 84.6% ± 3.9%. On the Cox regression analysis, the maximal aortic root diameter at initial presentation was the only significant predictor of aortic regurgitation and aortic root dilatation (hazard ratio, 1.10; 95% confidence interval, 1.02-1.19; P = .014).Conservative aortic root repair of acute type A aortic dissection demonstrates acceptable long-term clinical outcomes. However, more aggressive approaches should be considered for patients who have aortic root dilatation because of the risk of developing a root aneurysm after surgery.