Background <p>Spread through air spaces (STAS) has emerged as an independent prognostic factor in lung adenocarcinoma, yet its interaction with resection type remains poorly defined. We aimed to evaluate the prognostic impact of STAS on overall survival (OS) and disease-free survival (DFS) according to resection type in surgically resected lung adenocarcinoma.</p> Methods <p>We retrospectively analysed 252 patients who underwent resection for lung adenocarcinoma at a single institution between 2016 and 2023. Patients were stratified into four groups by STAS status and resection type. Overall survival and DFS were estimated using Kaplan-Meier analysis with log-rank testing. Multivariable Cox regression was performed to identify independent prognostic factors.</p> Results <p>STAS was present in 148 patients (58.7%). Among the four groups, patients who underwent STAS-positive sublobar resection demonstrated the worst prognosis, with a mortality rate of 50.0%, a median OS of 98 months, and a 5-year OS of 51.3%. STAS-positive lobar resection patients achieved a 5-year OS of 70.1%, comparable to STAS-negative lobar patients (67.8%). On multivariable Cox regression, STAS-positive sublobar resection was an independent predictor of mortality (HR 2.29, 95% CI 1.10–4.75; <i>p</i> = 0.026), as were lymphovascular invasion (HR 2.28; <i>p</i> = 0.001) and visceral pleural invasion (HR 2.14; <i>p</i> = 0.020). No significant difference in DFS was observed across groups (<i>p</i> = 0.963), suggesting that STAS primarily influences prognosis through its impact on overall survival rather than recurrence.</p> Conclusions <p>STAS positivity combined with sublobar resection independently predicts poor overall survival in lung adenocarcinoma. STAS status should inform surgical decision-making when sublobar resection is considered.</p>