Background:Significant tricuspid valve regurgitation (TR) is considered a poor prognosis factor for patients with hypoplastic left heart syndrome (HLHS). Performing a tricuspid valve plasty (TVP) during Norwood Stage I palliation (S1P) has rarely been reported. We report mid-term results of performing TVP during Norwood S1P.Methods and Results:Between December 2004 and July 2013, 48 patients with HLHS or variants underwent Norwood S1P and of them 11 (23%) with TR of a moderate degree or above underwent TVP. The estimated 1- and 5-year survival rates for Norwood S1P were 61% and 54%, respectively. Among the 11 patients with TVP, there were 2 early deaths. Nine patients had a Stage II operation and 3 of them died late. Four patients completed a Fontan operation, and 2 were waiting. Using Cox regression analysis, lower body weight, presence of intact atrial septum, and preoperative cardiopulmonary resuscitation were factors associated with increased risk for death. Patients with significant TR and undergoing TVP during Norwood S1P had a similar survival curve to those without significant TR.Conclusions:Our results for TVP performed during Norwood S1P were encouraging. They suggested that aggressive TVP is warranted in Norwood S1P when primary heart transplantation is not available. Further study is required to determine if the strategy does improve the results for patients with HLHS and TR initially. (Circ J 2016; 80: 1362–1370)