<p>Preterm and low birth weight (LBW) infants are at risk for cardiorespiratory instability in the semi-upright car seat position. Other “at-risk” infants include those with critical congenital heart disease (CCHD), though there are no formal recommendations for screening in this population. The objectives of this study were (1) to assess car seat tolerance screening (CSTS) practices in patients with CCHD at our institution and (2) to understand the epidemiology of this population, including incidence and risk factors for CSTS failure. We performed a retrospective medical record review of neonates with CCHD admitted between 2013 and 2020. Descriptive statistics and bivariate analyses were used to characterize CSTS performance and failure risks in this patient population. We identified 211 patients as having CCHD, of whom 171 infants underwent CSTS (81%) and 10 infants failed (6%). When comparing those who passed or failed their CSTS by cardiac lesion type (left heart, right heart, or mixing lesions), there were no statistically significant differences, nor did clinical or demographic characteristics predict failure. There were no significant differences in readmission or death within 30&#xa0;days of discharge. This is the largest study of CSTS exclusively in infants with CCHD. We identified a 6% failure rate, which is comparable to failure rates reported in preterm and LBW infants, suggesting that more formal recommendations for screening in this population are needed.</p>