To evaluate associations between postnatal imaging features and outcome of left-sided congenital diaphragmatic hernia, as defined by overall survival and a requirement for extracorporeal membrane oxygenation (ECMO). Newborns diagnosed prenatally with left-sided congenital diaphragmatic hernia between January 2013 and September 2021 were studied retrospectively. The esophageal deviation index was newly defined as the largest diameter from the midline to deviated gastric tube divided by the largest transverse diameter of the thoracic cavity on the radiograph. Regression analyses were performed to identify postnatal imaging features associated with overall survival and a requirement for ECMO. The predictive power (ie, area under the curve [AUC] of a time-dependent receiver operating characteristic curve) of prenatal, postnatal, and intraoperative findings for predicting survival were calculated. Ninety-seven patients (54 males; mean gestational age, 38.3 ± 1.9 weeks; mean birth weight, 2956.5 ± 540.0 g) were analyzed. The esophageal deviation index (adjusted hazard ratio [HR], moderate [≥0.19 to <0.24], 6.427 [P = .029]; severe [≥0.24], 33.007 [P < .001]) and right pneumothorax (adjusted HR, 8.763; P = .002) were associated with overall survival and with a requirement for ECMO. Liver herniation on postnatal ultrasound also was associated with overall survival (P < .001) and need for ECMO (P = .001). In addition, the AUC for prediction of 1-year survival from postnatal ultrasound was comparable with that of prenatally or intraoperatively detected liver herniation (0.93; 95% CI, 0.88-0.97). The esophageal deviation index, right pneumothorax, and liver herniation observed by postnatal imaging have prognostic value in patients with left-sided congenital diaphragmatic hernia.