Background: Poor growth is common in infants with a single ventricle. Lower weight-for-age z-score (WAZ) is associated with worse short-term outcome after bidirectional Glenn procedure. We sought to assess growth status at the time of the Fontan procedure and the effect of poor growth status on surgical outcomes. Methods: This retrospective case series examined children who underwent Fontan at our institution between January 2003 and December 2008. Weight and height were obtained at the time of admission for Fontan. Data from preoperative echocardiogram and cardiac catheterization were abstracted to document cardiac function and hemodynamic measurements. Outcome variables included ventilator time, chest tube duration, postoperative infections (bacteremia, mediastinitis, urinary tract infection, gastroenteritis, or culture-positive pneumonia), and length of hospital stay. Results: Fifty-five patients were included for analysis. The median age at Fontan was 46 months (range, 18 to 72); median WAZ was -1.0 (-3.8 to +2.0), and height for age z-score was -1.1 (-3.7 to +1.5). The WAZ was less than -2.0 in 19% of patients. Multivariable modeling revealed that patients with a WAZ less than -2.0 (p = 0.006) had a greater incidence of serious postoperative infections. The only factor predicting longer length of hospital stay was presence of a serious postoperative infection (p < 0.0001). Ventilator time was predicted only by length of cardiopulmonary bypass (p = 0.01). No factors were associated with longer chest tube duration. Conclusions: Growth failure in children with a single ventricle persists through presentation for Fontan. A WAZ less than -2.0 at Fontan is associated with a higher rate of serious postoperative infections, which are associated with longer length of hospital stay.