Aspergillus related sinusitis is a fungal infectious disease that, despite its diffusion, is still not well acknowledged to dental operators. Due to the anatomophysiology characteristics of the maxillary sinus, the diagnosis of non-invasive aspergillus sinusitis relies on clinical and imaging signs, and on the medical history of the patient. Here, we present a clinical case describing a fungus ball, which diagnosis resulted particularly difficult, due to the presence of concomitant dental interventions in the same maxillary area. A 50 years-old woman, without any medical issue, came to the private dental practice complaining about nasal discharge from the left side. Dental arch were subjected to several treatments; to better understand the working plan, an orthopantomogram was performed, revealing a radiopacity in the left sinus. The conebeam computed tomography showed the obstruction of the maxillary sinus, and clarified the presence of mycetoma calculus. The patient underwent surgical Caldwell-Luc intervention and mycetoma sampling; the following in-vitro investigations revealed the presence of Aspergillus Niger. The one-year followup showed no recurrence of the infection. The reported case is aimed to underline how mycetoma is a benign condition, still unknown to dentists despite its large diffusion. Moreover, the authors want to highlight that an endodontic treatment can offer a favourable environment to mycetoma formation.