Abstract Objective Stent graft-induced new entry (SINE) has been increasingly observed after thoracic endovascular aortic repair (TEVAR) for Stanford type B aortic dissection. SINE is often life threatening, and reintervention is required. This study investigated risk factors for SINE after TEVAR. Methods From July 2001 to June 2013, we retrospectively analyzed data from 79 patients who underwent TEVAR for Stanford type B aortic dissection. TEVAR was performed in 17 patients ≤2 weeks (acute) after the diagnosis of aortic dissection and in the remaining 62 patients >2 weeks (chronic) after diagnosis. Forty-two of the patients underwent TEVAR with modified stent graft with an “inwardly bent” margin, and the remaining 37 underwent TEVAR with a conventional stent graft. The maximal diameter, minimal diameter, mean diameter, circumference, and area of the true lumen were analyzed. Taper ratio and oversizing ratio were evaluated and compared between the SINE and non-SINE groups, and cutoff values of taper ratio and oversizing ratio for prediction of SINE were determined using receiver-operating characteristic curve analysis. The cumulative incidence of SINE was estimated with the Kaplan-Meier method. The multivariate Cox proportional hazards model was used to identify independent predictive variables for SINE. Results SINE occurred in 21 patients (26.5%) and occurred more frequently in patients with chronic dissection than in those with acute dissection (32.3% vs 5.9%; P  = .032). The Kaplan-Meier curves were significantly different ( P  = .016) between these groups. The incidence of SINE events was not significantly different between the modified stent group and nonmodified stent group (23.8% vs 36.0%; P  = .284). The taper ratio and oversizing ratio by maximal diameter, mean diameter, circumference, and area were significantly higher in the SINE group than in the non-SINE group, and Kaplan-Meier curves were significantly different between groups above and below optimal cutoff value ( P  < .0005 to .003). According to multivariate analysis, the hazard ratios of chronic aortic dissection were 6.30 (95% confidence interval, 0.83-47.74; P  = .075) to 7.80 (95% confidence interval, 1.03-59.07; P  = .047). The taper ratio and oversizing ratio calculated by maximal diameter, mean diameter, circumference, and area were independent predictors of the development of SINE. Conclusions Distal oversizing of the stent graft was an independent predictor of the development of SINE. Appropriate size selection of stent graft without distal oversizing might reduce the risk of late SINE events.