BACKGROUND This systematic review and meta-analysis synthesises evidence from both randomised trials and observational studies to determine whether lobectomy or sublobar resection offers improved outcomes for patients with stage Ia non-small cell lung cancer (NSCLC). METHODS Studies (up to June 2025) comparing lobectomy and sublobar resection (segmentectomy or wedge) for clinical stage Ia NSCLC (<2 cm) were included in the random-effects meta-analyses. Risk of bias was assessed using Risk of Bias 2 for randomised trials or Risk of Bias in Non-randomised Studies of Interventions-I for observational studies. RESULTS 19 studies, including four randomised trials, were included. Overall survival at 5 years was comparable between lobectomy and sublobar resection (HR=1.00; 95% CI 0.84 to 1.19; I²=26%), as was disease-free survival (HR=1.05; 95% CI 0.90 to 1.23; I²=0%). Sublobar resection was associated with significantly higher local recurrence (OR=1.86; 95% CI 1.07 to 3.25; I²=73%). No differences were observed in 10-year survival (OR=0.99; 95% CI 0.27 to 3.59; I²=86%) or postoperative change in forced expiratory volume in 1 s (mean difference=-4.70; 95% CI -11.15 to 1.76; I²=99%). In 10 studies that mandated systematic hilar and mediastinal lymph node sampling, sublobar resection was associated with improved overall survival compared with lobectomy (HR=0.81; 95% CI 0.69 to 0.965; I²=0%). CONCLUSIONS Lobectomy and sublobar resection offer comparable long-term survival for patients with stage Ia NSCLC. While sublobar resection is associated with higher local recurrence rates, subgroup analysis suggests that when intraoperative systematic hilar and mediastinal lymph node sampling is performed, sublobar resection may offer a survival advantage.