Malnutrition in critically ill patients is common in neonates and children, including those that receive extracorporeal life support (ECLS). We hypothesize that nutritional adequacy is highly variable, overall nutritional adequacy is poor, and enteral nutrition is underutilized in this population.A retrospective study of neonates and children (age<18 y) receiving ECLS at 5 centers from 2012 to 2014 was performed. Demographic, clinical, and outcome data were analyzed. Continuous variables are presented as median [IQR]. Adequate nutrition was defined as meeting 66% of daily caloric goals during ECLS support.Two hundred and eighty three patients received ECLS; the median age was 12 d [3 d, 16.4 y] and 47% were male. ECLS categories were neonatal pulmonary 33.9%, neonatal cardiac 25.1%, pediatric pulmonary 17.7%, and pediatric cardiac 23.3%. The predominant mode was venoarterial (70%). Mortality was 41%. Pre-ECLS enteral and parenteral nutrition was present in 80% and 71.5% of patients, respectively. The median percentage days of adequate caloric and protein nutrition were 50% [0, 78] and 67% [22, 86], respectively. The median percentage days with adequate caloric and protein nutrition by the enteral route alone was 22% [0, 65] and 0 [0, 50], respectively. Gastrointestinal complications occurred in 19.7% of patients including hemorrhage (4.2%), enterocolitis (2.5%), intra-abdominal hypertension or compartment syndrome (0.7%), and perforation (0.4%).Although nutritional delivery during ECLS is adequate, the use of enteral nutrition is low despite relatively infrequent observed gastrointestinal complications.