This paper shares a diagnostically challenging case of radiation-induced sarcoma that first presented as gingival ulcerations and pain in a postradiated nasopharyngeal carcinoma patient. Insufficient information from the clinical presentation and non-specific findings from initial imaging results hindered early diagnosis. Nonetheless, correlation with medical history, prompt histopathological analysis and PET-CT imaging eventually led to a definitive diagnosis. This case report aims to increase the awareness of this uncommonly known but deadly long-term complication of head and neck radiotherapy. Clinicians ought to include radiation-induced sarcoma in their list of differential diagnosis when a patient, with a history of head and neck radiotherapy, presents with persistent gingival or oral mucosa lesions, alveolar bony exposure or other suspicious dental-related symptoms.