Tricuspid valve regurgitation (TR) increases adverse outcomes in children with hypoplastic left heart syndrome (HLHS). Changes in tricuspid valve (TV) annulus and leaflet geometry have been described but the underlying causes for TR in HLHS remain uncertain. We aimed to examine the association between left ventricular (LV) size and TR in infants with HLHS as right ventricular (RV)-LV interactions may be important in TR development. Echocardiograms of 50 infants with HLHS were reviewed. LV size, RV function, TR grade, TV annulus z-score, and aortic arch obstruction were examined at birth and 1 year of age (or the latest study post-bidirectional Glenn anastomosis if the patient was < 1 year of age). 24/50 (48%) had severe LV hypoplasia and 26/50 (52%) had mild/moderate LV hypoplasia. At 1 year, 10/24 (42%) with severe LV hypoplasia had moderate/severe TR versus 0/26 in the mild/moderate LV hypoplasia group (p = 0.0002). TR progressed ( ≥ 1 grade) in 14/24(58%) with severe LV hypoplasia versus 5/26 (19%) with mild/moderate LV hypoplasia (p = 0.008). In this cohort, no association was found between the degree of TR and either RV function, TV annular z-score, or arch obstruction; or between the degree of LV hypoplasia and either RV function or TV annular z-score. In infants with HLHS, the severity and progression of TR is associated with the severity of LV hypoplasia. The mechanism for this association needs further exploration but suggests a role for RV-LV interactions in the development of TR.