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Lung adenocarcinoma exhibits diverse pathological features, some of which for example, histological grading and tumor spread through air spaces (STAS), can be used for prognosis. Extra-alveolar invasion (EX) is a unique pathological factor focused on depth of invasion, and is defined as tumor infiltration into periarterial, peribronchiolar, or interlobular septal stroma. We recently suggested EX as a prognostic indicator, but its significance in sublobar resection remains unclear. We investigated the prognostic impact of EX in 116 patients with pT1mi-pT2a non-mucinous lung adenocarcinoma treated by segmentectomy or wedge resection. EX was evaluated using elastic fiber staining. Among 10 recurrent cases, 8 were EX-positive, and 2 were EX-negative and STAS-positive. The EX(-)/STAS(+) cases had local recurrence, while the EX(+) cases exhibited metastatic recurrence. The pT1abc EX(+) group showed significantly shorter recurrence-free survival (RFS) than the pT1abc EX(-) group, but no significant differences were observed when compared with the pT2 group. EX(+ )/STAS(-) and EX(+ )/STAS(+) groups showed significantly shorter RFS than EX(-)/STAS(-) group, but EX(-)/STAS(+) group did not. In conclusion, EX was associated with poor prognosis after sublobar resection of lung adenocarcinoma. Combined evaluation of EX and STAS may improve postoperative risk stratification.