Purpose <p>The C-reactive protein (CRP)–albumin–lymphocyte (CALLY) index is a composite score that evaluates inflammatory and nutritional status. This study aimed to determine its prognostic significance in patients with resected lung cancer associated with interstitial pneumonia (IP).</p> Methods <p>Eighty-five patients with IP-associated resected lung cancers were included. The CALLY index was calculated as follows: (serum albumin × lymphocytes) / (CRP × 10⁴). The patients were classified into low and high CALLY groups based on a cutoff value determined by the receiver operating characteristic curve for overall survival (OS). The associations between the CALLY index, patient characteristics, and postoperative survival were retrospectively investigated.</p> Results <p>The postoperative hospital stay was significantly longer (<i>P</i> = 0.015) and the incidence of postoperative pneumonia was significantly higher (<i>P</i> = 0.004) in the low CALLY group (n = 20, 23.5%) than in the high CALLY group (n = 65, 82.5%). The recurrence-free survival (RFS) and OS were significantly poorer in the low CALLY group (<i>P</i> = 0.045 and<i> P</i> = 0.020, respectively). A multivariate analysis identified the CALLY index as an independent prognosticator factor for RFS and OS (<i>P</i> = 0.013 and<i> P</i> = 0.004, respectively).</p> Conclusion <p>The CALLY index is an independent prognostic factor in patients with IP-associated resected lung cancer.</p>