【Abstract】 Objective To investigate the impact of reduced respiratory muscle strength, assessed by peak expiratory flow rate (PEFR), on postoperative outcomes in patients with stage I-IIIA non-small cell lung cancer (NSCLC). Methods Clinical and imaging data of patients with stage I-IIIA NSCLC who underwent radical resection at our hospital from January 2020 to November 2025 were retrospectively analyzed, including PEFR (an indicator of respiratory muscle strength) based on pulmonary function tests and the pectoralis muscle index (PMI) derived from chest CT. The Jonckheere-Terpstra test and Spearman’s correlation analysis were used to evaluate age-related changes in PEFR and PMI and their correlation, respectively. Low PEFR was defined as values below the sex-specific lower quartile of PEFR. Univariate and multivariate Cox regression analyses were performed to assess the impact of PEFR and PMI on postoperative prognosis in NSCLC patients.Results A total of 102 patients were enrolled, with a median age of 62 years (range 53-67 years); 65 patients (63.7%) were male, and 24 (23.5%) were classified into the low PEFR group. The low PEFR group showed significant differences from the normal PEFR group in age, FEV1, DLCO, FEV1/FVC, FVC, serum albumin, and follow-up duration (all P < 0.05). In both male and female patients, PEFR progressively decreased with age and was positively correlated with PMI (r = 0.25, P = 0.001). Univariate and multivariate Cox regression analyses identified low PEFR as an independent risk factor for postoperative progression-free survival (PFS) in NSCLC patients (HR = 1.57, 95% CI: 1.03–2.39; P = 0.036).Conclusion Reduced respiratory muscle strength is an independent risk factor for postoperative PFS in NSCLC patients and may serve as an early biomarker for postoperative recurrence.