Aspergillosis is an opportunistic deep mycosis that occurs in immunocompromised patients, often in the paranasal sinuses. However, it sometimes occurs in healthy subjects, producing symptoms similar to those of a chronic sinusitis that is unresponsive to conventional treatment. A possible entry point for Aspergillus is the oroantral communication originated by perforation of the dental root cavity during root canal of a molar with penetration of material. We report the clinical case of a patient with symptoms of chronic sinusitis who was diagnosed as sinus aspergillosis after radiological and histological study. The origin may have been a third upper molar in which a root canal was performed.