Peripheral T-cell lymphomas (PTCLs) represent a rare and heterogeneous group of lymphoproliferative disorders, accounting for about 10% of non-Hodgkin lymphomas. While PTCLs typically present at nodal sites, extra nodal involvement is uncommon, particularly in the oral cavity. This case report presents a rare instance of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), manifesting as a persistent lesion on the lower lip in a 70-year-old male patient. The patient underwent multiple biopsies, which required immunohistochemical staining to confirm the diagnosis. Initial histopathological examinations raised suspicion of a lymphoproliferative disorder, with further testing revealing a 4.5 × 1.5 × 2.8 cm Fluorodeoxyglucose (FDG)-avid lesion on positron emission tomography (PET)/CT. The lesion was confirmed to be PTCL-NOS, characterised by positive CD3 and CD56 markers and a high Ki-67 proliferative index. Treatment involved six cycles of CHOEP chemotherapy followed by consolidative radiation therapy, delivering a total dose of 36 Gy. The patient responded well to treatment, with an interim PET scan showing a complete metabolic response (Deauville score of 3). Follow-up visits confirmed the absence of residual or recurrent disease. A teleconsultation a 6-month post-radiotherapy, along with an examination by a plastic surgeon, also showed no signs of recurrence. This case highlights the diagnostic challenges associated with PTCL at rare non-nodal sites and underscores the importance of a multidisciplinary approach in managing such cases. The patient remains in remission, with ongoing surveillance recommended for up to 5 years to monitor for potential disease recurrence. Further studies and long-term follow-up of similar cases are warranted to better understand the behaviour and optimal treatment strategies for PTCLs in rare extra nodal locations.