Objective: In treating pancreatic walled-off necrosis (WON), lumen-apposing metal stents (LAMS) have not proven superior to the traditional double pigtail technique (DPT). Among patients with large WON (>15 cm) and their associated substantial risk of treatment failure, the increased drainage capacity of a novel 20-mm LAMS might improve clinical outcomes. Hence, we conducted a study comparing the DPT and 20-mm LAMS in patients with large WON. Design: A single-centre, open-label, randomised, controlled superiority trial using an endoscopic step-up approach in patients with WON exceeding 15 cm in size. The primary endpoint was the number of necrosectomies needed to achieve clinical success (clinical and CT resolution), while the secondary endpoints included technical success, adverse events, length of stay and mortality. Results: Twenty-two patients were included in the DPT group and 20 in the LAMS group, with no significant differences in patient characteristics. The median size of WON was 24.1 cm (P25-P75: 19.6-31.1). The technical success rates were 100% for DPT and 95% for LAMS (p=0.48), while clinical success rates were 95.5% and 94.7%, respectively (p=1.0). The mean number of necrosectomies was 2.2 for DPT and 3.2 for LAMS (p=0.42). Five patients (12%) developed procedure-related serious adverse events (DPT=4, LAMS=1, p=0.35). The median length of stay was 43 (P25-P75: 40-67) and 58 days (P25-P75: 40-86) in the DPT and LAMS groups (p=0.71), respectively, with an overall mortality of 4.8%. Conclusions: For treating large WON, LAMS are not superior to DPT. The techniques are associated with comparable needs for necrosectomy and hospital stay, and no gross difference in adverse events. Trial registration number: NCT04057846.