There have been several reports on surgical interventions in patients with adult cervical spondylotic myelopathy associated with cerebral palsy. We performed posterior fusion with pedicle and/or lateral mass screws combined with preoperative intramuscular injections of botulinum toxin in two patients. Two weeks before the surgery, we injected the patients with the botulinum toxin to alleviate cervical pain and to reduce the involuntary movement associated with cerebral palsy. Surgical results were good in both patients without rigid external fixation. Both patients were able to undergo rehabilitation after the surgery as soon as possible without any complication. We think that our pre surgical treatment with botulinum toxin is a useful optional treatment for cervical spondylotic myelopathy associated with cerebral palsy.