This report concerns a 41-year-old female case of spinal muscular atrophy (SMA) associated with vocal cord paralysis. Her parents were not consanguineous. Her maternal grandmother and younger brother were suspected of having SMA. At age 37, she first experienced gait disturbance and began to have slowly progressive dysarthria and weakness of the extremities. Neurological examination revealed that she had inspiratory stridor, dysarthria and proximal muscular weakness of the extremities. Achilles tendon reflexes were absent, while there were no pathological reflexes or sensory disturbances. She showed a waddling gait and Gowers' sign. The laboratory data indicated mild elevation of serum CK. The nerve conduction study was normal, while the electromyographic study and muscle biopsy revealed neurogenic changes. We diagnosed the case as adult onset SMA of the autosomal dominant type. Laryngoscopy revealed that the patient had vocal cord paralysis, which was predominant in abductor muscles and of the posterior paralysis type according to the categories established by Isozaki. Genetic analysis showed no mutations in the genes of the neuronal apoptosis inhibitory protein and of the survival motor neuron.