Background: The feasibility of segmental resection for early-stage non-small cell lung cancer (NSCLC) is still controversial. This study aimed to compare survival outcomes following lobectomy and segmental resection in patients with pathological T1cN0M0 (tumor size 21–30 mm) NSCLC. Methods: Patients diagnosed between 1998 and 2016 with pathological stage IA NSCLC and with tumors measuring 21–30 mm were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. The observational outcomes were cancer-specific survival (CSS) and overall survival (OS) at 5 years. Univariate survival analysis was carried out to identify potential prognostic factors of prolonged survival. Cox proportional hazards model was used to adjust for confounding factors. Additionally, pairwise comparisons were conducted between lobectomy and segmental resection for CSS and OS, and forest plots were drawn. Results: Of the 9,580 patients analyzed, 400 patients (4.2%) underwent segmental resections. Patients with older age (P<0.001), smaller tumors (P<0.001), and left-sided tumors (P=0.002) were more likely to receive segmental resection. No difference was found in the operative mortality rates between the segmental resection group and the lobectomy group (1.0% vs. 1.2%, P=0.707). The CSS (HR, 1.429; 95% CI, 1.166–1.752; P=0.001) and OS (HR, 1.348; 95% CI, 1.176–1.544; P<0.001) in the segmental resection group were significantly worse than those in the lobectomy group. Subgroup analyses by age, year of diagnosis, sex, tumor size, histology, grade, and the number of dissected lymph nodes also confirmed that lobectomy was associated with improved CSS and OS. Conclusions: Lobectomy and thorough removal of lymph nodes should continue to be the recommended standard of care for patients with surgically resectable stage IA NSCLC with tumor size of 21–30 mm.