Patients with single ventricle heart disease after Fontan palliation are subject to progressive cardiovascular deterioration during adolescence. In this population, a peak oxygen consumption (V O2peak) less than 50% of predicted is an independent predictor of Fontan-related morbidity and mortality. A greater delay in postexercise V O2 recovery (VO2RD) is associated with worse outcomes in adults with heart failure, however, VO2RD has not been extensively studied in youth with Fontan (single ventricle) physiology. Purpose: The purpose of this study is to identify predictors and correlates of VO2RD in youth with Fontan. Methods: Cardiopulmonary exercise test data was used from a single center, cross-sectional study of children and adolescents (age, 8-21 yr) with Fontan physiology. The VO2RD was determined using time (s) to <90% of V O2peak and categorized as "low" (=10 s) or "high" (=10 s). t Tests and 2 analysis were used to compare continuous and categorical variables, respectively. Results: The analysis sample included 30 adolescents with Fontan physiology (age, 14.2 ± 2.4 yr; 67% male) with either right ventricular (RV) dominant (40%) or co/left ventricular (Co/LV) dominant (60%) systemic ventricular morphology. There were no differences in V O2peak between the high and low VO2RD groups (high = 1.3 ± 0.4 L·min-1; low = 1.3 ± 0.3 L·min-1; P = 0.97). VO2RD in participants with RV dominance was significantly greater than in patients with Co/LV dominance (RV = 23.8 ± 15.8 s; Co/LV = 11.8 ± 16.1 s; P = 0.03). Conclusions: V O2peak was not correlated with VO2RD when analyzed as high/low VO2RD groups. However, morphology of the systemic single ventricle (RV vs Co/LV) may be related to rate of recovery in V O2 after a peak cardiopulmonary exercise test.