Fungal infections associated with COVID-19 have been responsible for exacerbating the course of the disease, with mucormycosis being one of the main reported conditions. Although dental involvement is commonly considered an extension of rhinocerebral disease, some authors recognize it as a distinct clinical entity characterized by odontogenic onset mucormycosis. The aim of this study was to report the diagnosis of mucormycosis following drainage of odontogenic abscess in a post-COVID-19 diabetic patient. A 69-year-old post-COVID-19 diabetic man sought a maxillofacial surgery service due to complaints of pain and swelling on the right side of the face. Edema, dental mobility, and purulent discharge associated with teeth 16 and 17 were noted. It was observed that tooth 16 had undergone endodontic treatment, while tooth 17 exhibited pulp necrosis, both showing enlargement of the apical periodontal ligament space. Drainage of the odontogenic abscess was performed, and cone-beam computed tomography was requested. Tomographic findings included a suggestive image of osteolytic lesion in the posterior region of the maxilla extending into the right maxillary sinus. Extraction of teeth 16 and 17 and biopsy of areas of necrotic bone were performed. Histopathological examination revealed numerous large fungal hyphae forming right angles, positive for Grocott-Gomori staining, favoring the diagnosis of mucormycosis. The patient was referred for treatment with Amphotericin B and has been under follow-up for 3 years, with no need for additional interventions. The diagnosis of mucormycosis should be considered in immunosuppressed patients, especially those with diabetes mellitus and post-COVID-19, presenting signs and symptoms of odontogenic infection.