We report a previously healthy 8-year-old boy who presented to the hospital with a palpable abdominal mass, fever and abdominal pain. CT and MRI scans confirmed a large mass that was centered in the retroperitoneum. The lesion was biopsied and the histology showed branching hyphae. Tissue cultures grew Aspergillus fumigatus and a diagnosis of aspergilloma was made. The immunological work-up did not reveal an immunodeficiency. This case is a unique presentation of aspergilloma presenting in an unusual location and in an immunocompetent patient.