Purpose: Patient-reported outcome (PRO)-based symptom assessment with a threshold can facilitate the early alert of adverse events. The purpose of this study was to determine whether shortness of breath (SOB) on postoperative day 1 (POD1) can inform postoperative pulmonary complications (PPCs) for patients after lung cancer (LC) surgery. Methods: Data were extracted from a prospective cohort study of patients with LC surgery. Symptoms were assessed by the MD Anderson Symptom Inventory-lung cancer module (MDASI-LC) before and daily after surgery. Types and grades of complications during hospitalization were recorded. SOB and other symptoms were tested for a possible association with PPCs by logistic regression models. Optimal cutpoints of SOB were derived, using the presence of PPCs as an anchor. Results: Among 401 patients with complete POD1 MDASI-LC and records on postoperative complications, 46 (11.5%) patients reported Clavien-Dindo grade II-IV PPCs. Logistic regression revealed that higher SOB score on POD1 (odds ratio [OR]=1.13, 95% CI=1.01-1.27), male (OR=2.86, 95% CI=1.32-6.23), open surgery (OR=3.03, 95% CI=1.49-6.14), and lower forced expiratory volume in one second (OR=1.78, 95% CI=1.66-2.96) were significantly associated with PPCs. The optimal cutpoint was 6 (on a 0-10 scale) for SOB. Patients reporting SOB < 6 on POD1 had shorter postoperative length of stay than those reporting 6 or greater SOB (median, 6 vs 7, P =0.007). Conclusion: SOB on POD1 can inform the onset of PPCs in patients after lung cancer surgery. PRO-based symptom assessment with a clinically meaningful threshold could alert clinicians for the early management of PPCs.