Cervical spinal cord injury can result in dysphagia and tetraplegia. Dysphagia therapy can be required to avoid aspiration pneumonia during oral intake for persons with cervical spinal cord injury. Complete lateral decubitus position may be a specific position for safe swallowing. However, the literature on dysphagia therapy in complete lateral decubitus position for persons with tetraplegia and dysphagia is limited. We present the case of a 76-year-old man with dysphagia and tetraplegia secondary to cervical cord injury. As the patient wished for oral intake, swallowing training in an elevated position of the head at 60° was already initiated. Two days after admission, aspiration pneumonia occurred. As the spasticity increased continuously, the patient could not comfortably undertake swallowing training in an elevated head position of 60°. The flexible endoscopic evaluation of swallowing (FEES) was performed for the patient. The patient did not swallow water or jelly safely in an elevated head position. However, the patient swallowed jelly safely in the right complete lateral decubitus position. Two months after the initiation of oral intake in the right complete lateral decubitus position, the second FEES revealed that the patient swallowed jelly and food in the form of paste safely in the left complete lateral decubitus position. To relieve the pain of the right shoulder induced by continuous right complete lateral decubitus position, the patient retained oral intake in the left or right complete lateral decubitus position alternately for six months without recurrent aspiration pneumonia. Right and left complete lateral decubitus positions when alternately performed in swallowing training can be useful and safe for a patient with dysphagia and tetraplegia secondary to cervical spinal cord injury.