Background: Maxillary sinus fungal ball is a common cause of unilateral maxillary sinusitis. Fungal balls or mycetomas are primarily treated with surgery to remove the fungus. However, this assumes the pre-fungal ball sinus cavity was normal and post-surgery patients may suffer from mucostasis in the sinus cavity with persistent symptoms. It is proposed that fungal balls are potentially a feature of impaired mucus clearance as they are a pathology in their own right. Methods: A case series of consecutive patients undergoing antrostomy for maxillary sinus fungal ball was performed. Patient factors including age, gender, smoking status, comorbidities (allergy, asthma, and reflux), disease specific factors including duration of symptoms, microbiology (bacterial co-infection, Gram-positive and/or Gram-negative) and preoperative radiologic findings (extent of sinus development, and neo-osteogenesis/bone thickness) were collected. The primary outcome was sinus function defined by evidence of a normal functioning maxillary sinus, with the absence of mucostasis or pooling, on endoscopic exam at three months, six months and last follow-up. Endoscopic evaluation of inflammation was also collected. Results: 28 patients (age 58.5 ± 15.5 years, 64.3% female) were assessed. Mucostasis was present at three months in 39.3%, at six months in 32.1%, and 17.9% at last follow-up. There was no comorbidity or radiologic finding that was associated with failure to normalize. Those patients with mucostasis had a higher modified Lund-Mackay endoscopic score at last follow-up (5.0 ± 0.7 v 0.2 ± 0.6, p < 0.01). Conclusions: Long term post-operative mucostasis occurred in 17.9% of patients following an adequate maxillary antrostomy for treatment of a fungal ball. Patients with mucostasis had persistent mucosal inflammation and a greater need for further surgery (modified medial maxillectomy).