BACKGROUND: The prognostic nutritional index (PNI), calculated as 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (cells/mm3), can reportedly predict postoperative complications and prognosis for various types of malignancy. However, the clinical significance and prognostic value of the PNI for both short- and long-term outcomes remains uncertain in patients with lung cancer. METHODS: We retrospectively reviewed 248 patients with completely resected non-small cell lung cancer (NSCLC). Clinicopathologic characteristics were evaluated according to the PNI, and the prognostic significance for postoperative outcomes was assessed using Cox proportional regression analysis. The survival rate was calculated using the Kaplan-Meier method. RESULTS: An optimal cutoff of 48 for recurrence-free survival (RFS) was determined using the minimum p value approach. Old age, low body mass index, large tumor size, and elevated C-reactive protein levels correlated significantly with low PNI. Logistic regression analysis demonstrated that low PNI status was statistically related to postoperative complications (Clavien-Dindo grade ≥II) and pulmonary air leakage. Five-year overall survival (OR) rates in the high- and low-PNI groups were 80.6% and 58.5%, respectively (p = 0.002). Five-year RFS rates were 73.6% and 48.6%, respectively (p < 0.001). Furthermore, PNI was identified as an independent prognostic factor for OS (hazard ratio [HR], 2.18; 95% confidence interval [CI], 1.08-4.21) and RFS (HR, 2.57; 95% CI, 1.46-4.38) by multivariate analysis. CONCLUSIONS: The PNI could represent a useful biomarker to predict postoperative complications and survival in patients with completely resected NSCLC.