Neoscytalidium dimidiatum is a rare dematiaceous fungus that was first described in 1916 as Dothiorella mangiferae. From the standpoint of epidemiology and therapy, early detection of fungal rhinosinusitis (FRS), the causative agents, and their associated risk factors can improve the therapeutic outcome and decrease the mortality rates among patients. In this study, we report a 34-year-old Iranian female patient with allergic bronchopulmonary aspergillosis (ABPA), who presented to our facility with an 8-year history of chronic fungal sinusitis, drug-resistant asthma, pneumonia, bronchitis, post-nasal discharge, nasal obstruction, nasal polyposis, and anemia. The patient was subjected to diagnostic nasal endoscopy and computed tomography (CT) scan of paranasal sinuses, as well as routine, complementary mycological, and molecular methods, which confirmed the diagnosis of allergic fungal rhinosinusitis in patients with ABPA. Neoscytalidium dimidiatum was isolated from the sinus of the patient. Results of in vitro susceptibility tests indicated that the case isolate was susceptible to amphotericin B and itraconazole at concentrations which are commonly achieved in patients receiving recommended dosages for invasive mycoses (0.25 to 0.75 mg/kg of body weight daily for amphotericin B and 100 to 400 mg daily for itraconazole) and resistant in vitro to caspofungin, voriconazole, and posaconazole. The patient was successfully treated with amphotericin B / itraconazole + postoperative oral corticosteroids (OCS). Neoscytalidium dimidiatum infection should be considered as a possible additional factor in the etiology of AFRS, especially in immunocompromised patients.