BACKGROUND Congenital tracheal stenosis (CTS) is a rare and life-threatening disease in children. Although pulmonary artery sling (PA sling) complicated by CTS sometimes occurs, there are few reports detailing the management of CTS with PA sling. The purpose of this retrospective study was to determine the appropriate indications for surgical intervention for CTS complicated by PA sling. METHODS We evaluated 42 patients (19 males and 23 females) with the median age of 9.9±3.3 months (range, 5-34 months) with CTS complicated by PA sling who were treated at our hospital between 2005 and 2018. Twenty-eight patients received both a slide tracheoplasty and PA re-implantation, and 14 patients were managed conservatively for CTS. Among the latter, nine patients received PA re-implantation only, and five were managed conservatively without any surgery. We determined the surgical indications by retrospectively comparing the DLR value [tracheal diameter (mm)/stenotic length ratio], history of ventilator respiration, mortality rate, and post-operative course of patients at a single institution. RESULTS The cut-off value for the DLR was determined to be 5.9 (sensitivity: 0.929, specificity: 0.714) by using the ROC curve (AUC 0.89, P<0.05). CONCLUSIONS A DLR value under 5.9 may serve as a new surgical indication for CTS complicated by PA sling.