Background: Maxillary sinus fungus ball (MSFB) is a non-invasive form of fungal rhinosinusitis characterized by an accumulation of fungal material within the sinus lumen without tissue invasion. Clinical manifestations are often non-specific, whereas computed tomography (CT) may provide important diagnostic clues. Methods: We describe five patients with clinical and radiological findings suggestive of MSFB who underwent endoscopic sinus surgery. Clinical manifestations, nasal endoscopic findings, CT features, histopathological and/or mycological results, and surgical management were reviewed. Results: The patients ranged from 29 to 66 years of age. All lesions were unilateral and involved the maxillary sinus. Purulent nasal discharge and headache were the predominant symptoms. CT demonstrated maxillary sinus opacification or mucosal thickening associated with intralesional calcifications in all patients. All patients underwent endoscopic maxillary sinus surgery. Fungal culture was negative in three patients and positive for filamentous fungi in one patient; histopathological examination in the remaining patient showed inflammatory tissue. Conclusions: MSFB should be considered in persistent unilateral maxillary sinus disease, particularly when CT demonstrates intralesional hyperattenuation or calcification. Negative fungal culture does not exclude MSFB. Diagnosis should integrate clinical, endoscopic, radiological, intraoperative, histopathological, and mycological findings. Endoscopic sinus surgery remains the treatment of choice for symptomatic disease.