Sinus bone grafts have been used successfully to augment atrophic posterior maxilla for dental implant placement. Even though sinus bone grafting is generally considered to be a safe surgical procedure, postoperative maxillary sinus infections can occur and therefore need to be considered. Bacteria, as well as viruses and fungi, have been identified as causative agents. Because fungal infection of the maxillary sinus after sinus bone grafting is not well known, we report a case of a middle-aged male patient along with the clinical, radiographic, and histologic findings. The patient was referred from his private dentist because of failed sinus bone grafting and osseointegration of implants. The surgical approach to the sinus yielded a friable mass of brownish-red material from the sinus. Review of pathology slides revealed a noninvasive hyphal mass caused by Aspergillus and polypous mucosa. After surgical removal of the mycotic masses, sinus bone grafting, using allograft, was performed. Bone formation after the healing period was favorable and dental implants were placed. There was no recurrence of fungal sinusitis.