Objectives: Compare the impact of initial extubation to positive airway pressure versus high-flow nasal cannula on postoperative outcomes in neonates and infants after congenital heart surgery. Design: Retrospective cohort study with propensity-matched analysis. Setting: Cardiac ICU within a tertiary care children's hospital. Patients: Patients less than 6 months old initially extubated to either high-flow nasal cannula or positive airway pressure after cardiac surgery with cardiopulmonary bypass were included (July 2012 to December 2015). Interventions: None. Measurements and Main Results: Of 258 encounters, propensity matching identified 49 pairings of patients extubated to high-flow nasal cannula versus positive airway pressure. Extubation failure was 12% for all screened encounters. After matching, there was no difference in extubation failure rate between groups (positive airway pressure 16% vs high-flow nasal cannula 10%; p = 0.549). However, compared with high-flow nasal cannula, patients initially extubated to positive airway pressure experienced greater resource utilization: longer time to low-flow nasal cannula (83 vs 28 hr; p = 0.006); longer time to room air (159 vs 110 hr; p = 0.013); and longer postsurgical hospital length of stay (22 vs 14 d; p = 0.015). Conclusions: In this pediatric cohort, primary extubation to positive airway pressure was not superior to high-flow nasal cannula with respect to prevention of extubation failure after congenital heart surgery. Compared with high-flow nasal cannula, use of positive airway pressure was associated with increased hospital resource utilization. Prospective initiatives aimed at establishing best clinical practice for postoperative noninvasive respiratory support are needed.