Iliac aneurysms are rare in children, especially mycotic aneurysms. Re-vascularization is challenging given the infected field and concern on patency due to their growth potential and a longer life-span. We report a complex case of a mycotic iliac aneurysm in a child. A 12-years-old boy with a previous history of infective endocarditis was referred to us for a right common iliac mycotic aneurysm after presenting with pain. A balloon-expandable stent-graft was deployed across the aneurysm during the acute presentation. He improved post-operatively, but developed abdominal pain four weeks later. A repeat computed tomography (CT) imaging showed a new inflammation of the appendix which was adhered to the calcified wall of the aneurysm and an endoleak from the internal iliac artery. A laparotomy was performed and the right internal iliac artery ligated along with an appendicectomy and omental pedicle. Postoperatively the patient was well and discharged home. Six-month surveillance revealed a healthy child and imaging showed a patent stent-graft and no residual collection.