Introduction: Type 1A (T1A) endoleak is a critical complication following endovascular repair of abdominal aortic aneurysms (EVAR), marked by persistent blood flow outside the endograft due to inadequate sealing of the proximal landing zone. This phenomenon poses significant challenges necessitating prompt intervention given its direct correlation with an increased risk of AAA sac expansion and rupture. Incidence of T1A endoleak varies widely, and accounts for about 1.1% of AAA ruptures post-EVAR. Finding durable interventions remain a challenge and this study aims to review the effectiveness of current treatment options. Methods: A retrospective cohort study was performed in all patients who had EVAR over a 15 year period in a major Australian tertiary institution. Aneurysm characteristics were collected and analysed such as proximal neck diameter/length, angulation, conical neck and extent of calcification and mural thrombus. Interventions included endoanchors, embolization with coils and glue, cuff extension, fenestrated and chimney grafts, and additional stents. Results: Thirty-seven patients were identified with a mix of early and late presentations of T1A endoleak. There were no statistically significant factors contributing to increased risk of T1A endoleak identified. Extension cuffs with or without endoanchors were most effective in treating early onset endoleaks, but had a high failure rate in late onset presentations. Patients with late onset endoleaks treated with a fenestrated graft demonstrated durable outcomes. Conclusion: Durable treatment of T1A endoleak remains challenging. While durable treatment of early onset endoleaks can be achieved with extension cuffs, late onset endoleaks require a fenestrated graft for a durable outcome.