Synovial cysts of the cervical spine, although they occur infrequently, may cause acute radiculopathy or myelopathy. Here, we report a case of a cervical synovial cyst presenting as acute myelopathy after manual stretching. A 68-year-old man presented with gait disturbance, decreased touch senses, and increased sensitivity to pain below T12 level. These symptoms developed after manual stretching 3 days prior. Computed tomography scanning and magnetic resonance imaging revealed a 1-cm, small multilocular cystic lesion in the spinal canal with cord compression at the C7-T1 level. We performed a left partial laminectomy of C7 and T1 using a posterior approach and completely removed the cystic mass. Histological examination of the resected mass revealed fibrous tissue fragments with amorphous materials and granulation tissue compatible with a synovial cyst. The patient's symptoms resolved after surgery. We describe a case of acute myelopathy caused by a cervical synovial cyst that was treated by surgical excision. Although cervical synovial cysts are often associated with degenerative facet joints, clinicians should be aware of the possibility that these cysts can cause acute neurologic symptoms.