Glioneuronal tumor with neuropil-like islands (GTNI) is considered a rare variant of astrocytoma, characterized by discrete aggregates of cells expressing neuronal markers that punctuate a GFAP-positive glial background. Of the 24 published GTNI cases, only two occurred in adult spinal cords; none occurred concurrent with another CNS tumor; and none of those tested exhibited the 1p/19q deletion typical of oligodendroglioma. A 48-year-old man without significant past medical history was diagnosed with a WHO grade II oligodendroglioma by stereotactic biopsy of a lesion discovered after the patient suffered a generalized tonic-clonic seizure. By FISH analysis, this tumor exhibited the 1p/19q deletion present in up to 80% of oligodendrogliomas. The patient received 14 monthly cycles of temozolomide, and his cerebral tumor had a minor response. When the patient subsequently reported progressive paresthesias of his lower extremities, an MRI revealed an enhancing, cystic tumor of the thoracic spinal cord that was diagnosed as GTNI by histological analysis. By FISH analysis, this lesion exhibited the same 1p/19q deletion present in the concurrent cerebral oligodendroglioma. This case of a spinal cord GTNI with 1p/19q deletions constitutes the third report of a spinal cord GTNI in an adult patient; the first report of a GTNI in an individual with a separate CNS neoplasm; and the first report of a GTNI with 1p/19q deletions. This case establishes a potential genetic kinship between GTNI and oligodendroglioma that warrants further investigation.