Retro-odontoid pseudotumor is an inflammatory mass most frequently associated with rheumatoid arthritis and dialysis. Recently, some case reports of retro-odontoid pseudotumor without instability have been published. Here we describe a 63-year-old man who was admitted to our hospital with numbness of the left upper extremity and walking disturbance. MRI showed a large retro-odontoid pseudotumor and severe compression of the spinal cord at the C1 level. The patient underwent C1 laminectomy, posterior occipital-C2 fusion and tumor resection via a transdural approach. Postoperative MRI showed that the retro-odontoid pseudotumor had been partially removed, but this was enough to obtain sufficient decompression of the spinal cord. Neurological symptoms were markedly improved after surgery.