A 12-year-old female, neutered German shepherd dog developed progressive hindlimb followed by forelimb ataxia leading to tetraplegia. Neurological examination suggested lower motor dysfunction. Biochemical evaluation revealed a monoclonal hypergammaglobulinaemia, hypoalbuminaemia and hypercalcaemia. Multiple lytic lesions were identified radiographically in numerous bones. A bone marrow aspirate confirmed the diagnosis of multiple myeloma, with large numbers of plasma cells seen in clusters. An electromyogram revealed positive sharp waves and fibrillation potentials in the skeletal muscles of the limbs, suggesting a polyneuropathy. The dog was treated with chemotherapy using melphalan and prednisolone. Both the hypergammaglobulinaemia and the polyneuropathy resolved and the dog had normal motor function four weeks after commencing treatment. Polyneuropathy may occur as a paraneoplastic syndrome secondary to myeloma, and in this case was reversible following treatment of the underlying disease.