Non-Hodgkin lymphomas (NHLs) are a heterogeneous group of malignancies originating from the lymphoid tissues, which can be differentiated by distinct epidemiology, etiology, and clinical characteristics. They can occur in the lymph nodes or as extranodal lesions. The vast majority of extranodal oral NHLs are classified as diffuse large B-cell lymphomas (DLBCL). They are usually found in the maxilla and they rarely occur in the mandible. The aim of this paper was to report a case of NHL with mandibular location by detailing its different clinical, radiological, and histopathological aspects. Herein, we report a case of NHL in the under chin region of the mandible in a 66-year-old male patient. The first diagnosis was post-extraction complication with delayed bone healing. The clinical and standard radiological examinations had no pathognomonic features. However, left labio-chin hypoesthesia and CT examination revealed a malignancy of the lesion without any precision. After performing further diagnostic examinations, including a subsequent biopsy, diagnosis of diffuse large B-cell lymphoma (DLBCL) was made. The patient was therefore treated with chemotherapy and he showed a satisfactory outcome for more than 5 years. Intraoral lymphomas may mimic odontogenic lesions; hence it is important for the dentist to be aware of the various manifestations of NHL to avoid delay and inappropriate treatment strategies.