Overcrowding scores have been studied extensively in adult emergency departments (EDs), but few studies have determined utility in the pediatric setting. The objective of this study was to determine the association between a modified National Emergency Department Overcrowding Score (mNEDOCS) and established ED metrics in a large academic tertiary care pediatric ED. NEDOCS was modified to increase applicability in the pediatric setting by including the number of patients in resuscitation rooms instead of a number of patients on ventilators. Patient characteristics, ED disposition, ED length of stay (LOS), rate of left without being seen (LWBS), hospital LOS (HLOS), ED returns within 72 hours, and mNEDOCS were acquired retrospectively for every ED encounter in 2016-2019 using the electronic health record. Descriptive statistics, Spearman correlation, and multivariate analyses were calculated to evaluate the association between specific ED metrics and mNEDOCS. Modified NEDOCS positively correlated with ED LOS, LWBS, and rate of 72-hour return visits. A negative correlation was found between mNEDOCS and HLOS. When controlling for select covariates, the odds of LWBS doubled with each increase in mNEDOCS category (odds ratio, 2.03; 95% confidence interval [CI], 2.00-2.06), ED LOS was associated with an increase of 27 minutes as mNEDOCS category increased (β = 26.80; 95% CI, 26.44-27.16), and the odds of 72-hour return visits increased by 6% when mNEDOCS increased by one category (odds ratio, 1.06; 95% CI, 1.05-1.07). Hospital LOS was associated with a 100-minute decrease per increase in mNEDOCS category (β = -99.85; 95% CI, -180.68 to -18.48) when controlling for covariates. Modified NEDOCS is positively associated with ED LOS, LWBS, and 72-hour return visits, consistent with adult data. Further investigation is needed to elucidate the association between mNEDOCS and HLOS. This study illustrates the utility of mNEDOCS as a measure of overcrowding in a pediatric ED.