Purpose <p>Metastatic intramedullary spinal cord tumors generally have poor prognosis, with chemotherapy often deemed ineffective. We report about a patient who achieved a favorable outcome with an immune checkpoint inhibitor following the resection of the extramedullary component of a metastatic intramedullary tumor.</p> Method <p>A 74-year-old man underwent upper lobectomy for lung cancer. Seven months after surgery, he developed urinary retention and walking difficulty. Contrast-enhanced magnetic resonance imaging (MRI) revealed an intradural extramedullary tumor with homogeneous enhancement at the C7/Th1 level. Emergent tumor resection was performed.</p> Results <p>Intraoperatively, a part of the tumor was found to be firmly adhered to the spinal cord. The tumor was resected, and the adhered portion was cauterized. Postoperatively, the patient’s paraparesis improved, enabling him to walk with a cane. Histopathological analysis confirmed the tumor as a metastasis of lung cancer. Postoperative MRI revealed residual intramedullary lesions, leading to a metastatic intramedullary tumor diagnosis. Given the high PD-L1 expression in the tumor cells, treatment with an immune checkpoint inhibitor was initiated. This resulted in the resolution of spinal cord edema and residual tumor disappearance on follow-up MRI. The patient maintained ambulatory function for 2 years.</p> Conclusion <p>Recent studies have demonstrated the efficacy of immune checkpoint inhibitors for brain metastases of lung cancer with high PD-L1 expression. In our case, spinal cord edema resolved, and the residual tumor regressed, with good neurological function sustained over 2 years. These findings suggest that immune checkpoint inhibitors may also be effective for metastatic intramedullary spinal cord tumors.</p>