Recent studies have reported that sublobar resection is not inferior to lobectomy for small-sized non-invasive adenocarcinoma (ADC); however, the adequacy for small-sized invasive ADC (IAD) remains unclear. The objective of this study was to identify prognostic factors and validate sublobar resection for small-sized IAD. We retrospectively reviewed patients with therapy-naïve, pathological stage I (≤2-cm) IAD, who had undergone complete resection from 1998-2015. Each tumor was evaluated by comprehensive histologic subtyping according to the 2015 World Health Organization classification. Overall survival (OS) and recurrence-free survival (RFS) was estimated using the Kaplan-Meier method. 179 patients met inclusion criteria. 104 (58%) were male and 75 (42%) were female, with a median age of 68 years; sublobar resection was performed in 35 (20%), and lobectomy or pneumonectomy in 144 (80%). Median pathological tumor size was 1.5 cm, with a median invasive component size of 0.9 cm, and pleural, lymphatic, or vascular invasion in 27 (15%), 25 (14%), and 49 (23%) patients, respectively. In IAD, the elderly patients and ever smokers were likely to undergo sublobar resection (p=0.015, 0.011, respectively). Patients undergoing sublobar resection for IAD had significantly worse prognosis (5-year OS: 59.9%, 90.2%, p<0.0001) and increased risk of local recurrence (5-year RFS: 60.0%, 87.6%, p<0.0001). Multivariable analysis revealed that sublobar resection, age, and sex was an independent risk factor of overall survival and sublobar resection and vascular invasion was an independent risk factor of recurrence for IAD ≤2-cm. Sublobar resection in patients with IAD ≤2-cm was significantly associated with increased risk of recurrence and worse prognosis.