Paraneoplastic syndromes have only been reported in malignant pleural mesothelioma (MPM) in a few cases. In this case, we describe a 57-year-old man with MPM who developed sensory-motor polyneuropathy 18 days after diagnosis. Thorough endocrinological, neurological, and paraclinical examinations gave no explanation of the symptoms, and paraneoplasia was therefore suspected. The patient was treated with immunoglobulin and prednisolone, and this resulted in subjective, objective, and paraclinical improvement of the symptoms. We therefore suggest that polyneuropathy is a possible paraneoplastic syndrome in MPM.