Castleman's disease is a rare clinicopathological entity characterized by multicentric angiofollicular lymph node hyperplasia. Peripheral neuropathy has infrequently been described in patients with Castleman's disease. A patient is described who presented initially with severe painful sensorimotor polyneuropathy of his lower limbs diagnosed as a plasma cell variant of Castleman's disease associated with features of POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin change). The patient was treated with plasmapheresis, immunosuppressive agents, and intensive rehabilitation. His functional status improved from being wheelchair bound to ambulating independently with crutches. Clinicians should be alert to the relationship of Castleman's disease and mixed polyneuropathy because physical improvement is possible with treatment. Also, the evaluation of patients presenting with peripheral neuropathy of unknown etiology and lymphadenopathy should include lymph node biopsy to rule out Castleman's disease.