Purpose: Duplex ultrasound (DUS) surveillance following femoropopliteal endovascular therapy (EVT) is widely practised to detect restenosis and guide pre-emptive reintervention. An ANZSVS survey confirmed 83% of vascular surgeons perform routine post-EVT DUS surveillance, yet this resource-intensive practice lacks adequately powered randomised evidence. SURVEIL aims to determine whether routine DUS surveillance reduces target vessel occlusion, major adverse limb events (MALE), and death compared to clinical surveillance alone. Methodology: SURVEIL is a multicentre, open-label, superiority randomised controlled trial across vascular surgery units in Australia and New Zealand (HREC: 2025/ETH01129; ACTRN12625000889459). Adults with a patent femoropopliteal target vessel at 4–6 weeks post-EVT for symptomatic PAD are randomised 2:1 to DUS plus clinical surveillance versus clinical surveillance alone. Both arms undergo clinical assessment and ankle-brachial pressure index measurement at 3, 6, 9, 12, 18, and 24 months. The primary endpoint is freedom from a composite of target vessel occlusion, MALE, or death at 24 months, analysed by Kaplan–Meier methods and log-rank test (intention-to-treat). Secondary endpoints include target lesion revascularisation, patency, symptomatic improvement, quality of life, and cost-effectiveness. A sample size of 288 achieves 90% power to detect a 20 percentage-point difference, with an adaptive interim analysis permitting up to 50% sample size increase. Results: Recruitment commenced in 2026. Results are anticipated following 24-month follow-up of all enrolled participants. Conclusion: SURVEIL is the first pre-registered, adequately powered, multicentre RCT evaluating DUS surveillance following femoropopliteal EVT for the full clinical spectrum of symptomatic PAD. Results will directly inform international clinical guidelines and healthcare resource allocation.