Introduction: Recurrent oral squamous cell carcinoma (SCC) poses significant challenges in treatment, requiring a multifaceted approach for effective management. Case Presentation: We present the case of a 68-year-old patient with a history of keratonizing SCC of the mandibular gingiva, treated with surgical resection, adjuvant radiotherapy (RT) to a total dose of 60 Gy in 30 fractions and 6 cycles of concurrent chemotherapy. After 6 years of follow-up, the patient experienced a local late recurrence in clinical stage rT4N0M0 requiring palliative chemotherapy (6 cycles of PF regimen). Due to progression, nivolumab-based immunotherapy was administered. After the 11th cycle of immunotherapy, high-dose re-irradiation (18 Gy in 3 fractions) was applied due to subsequent progression. The addition of stereotactic RT to the immunotherapy allowed nivolumab to be continued until cycle 64, ensuring long-term disease stabilization with acceptable tolerability. Consecutive palliative chemotherapy included paclitaxel and methotrexate. Conclusion: This case highlights the complex management of recurrent oral SCC, emphasizing the role of combining stereotactic RT with nivolumab in prolonging the administration of immunotherapy.