Spread through air spaces (STAS) has been identified as an invasion pattern in non–small cell lung cancer (NSCLC). This study evaluated the association between tumor STAS and various clinicopathological parameters of NSCLC, with emphasis on the prognostic role of STAS. Methods: We evaluated 96 cases of NSCLC for STAS. STAS-positive cases were graded according to the distance between the edge of the primary tumor and the furthest STAS, in millimeters, or the number of alveoli separating STAS from the tumor. Results: STAS was observed in 33 patients (34.4%). In 28 cases, STAS was located in airspaces >3 alveoli away from the primary tumor. In 18 cases, STAS was found in airspaces > 2.5 mm away from the edge of the primary tumor. Morphologically, 18 cases of STAS demonstrated a solid nest pattern, eight showed a micropapillary cluster pattern, and seven exhibited a single-cell pattern. In multivariate analysis, only high tumor grade (p = .001) was independently associated with STAS in NSCLC. The presence of STAS (p = .047), lymphovascular invasion (p = .001), positive surgical margin (p = .021), adenocarcinoma histology (p = .020), and postoperative therapy (p = .049) showed a statistically significant lower overall survival (OS). However, multivariate analyses showed that STAS is not an independent predictor of OS in NSCLC. In addition, STAS-positive cases with an extension of >2.5 mm had significantly lower disease-free survival (DFS) (p = .018). Conclusions: The findings demonstrated that STAS is independently associated with a higher tumor grade and appears to have an adverse impact on OS and DFS in the examined subpopulation.