BACKGROUND: Pulmonary mucinous adenocarcinoma (PMA), a rare type of adenocarcinoma, remains controversial in terms of its associated prognosis. We conducted this study to compare the oncological outcomes of lobectomy and sublobectomy for peripheral small-sized PMA. METHODS: This retrospective observational study included all patients with peripheral small-sized (≤2 cm) clinical stage IA1-A2 PMA who underwent lobectomy or sublobectomy (with margin distances ≥2 cm or greater than tumor diameter) between January 2015 and December 2018. Recurrence-free survival (RFS) and overall survival (OS) were compared between the lobectomy and sublobectomy groups with Kaplan-Meier curves and log-rank tests. RESULTS: This study examined 279 patients, with 176 cases in the lobectomy group and 103 cases in the sublobectomy group. Recurrence occurred in 8 patients, and 6 patients died. Before and after propensity score matching (PSM), log-rank tests showed no statistical differences between the lobectomy and sublobectomy groups in terms of 5-year RFS (before PSM: 97.0% CONCLUSIONS: For peripheral small-sized PMA, sublobectomy yielded an RFS and OS comparable to those of lobectomy.