Malignant mesothelioma of the tunica vaginalis testis is a rare and aggressive asbestos-related malignancy that may pose difficult diagnostic problems. After 16 years of asbestos exposure, a 38-year-old petrochemical worker came to our notice with acute right testicular pain and swelling, simulating torsion of the spermatic cord. Histopathology of surgical samples of the tunica vaginalis revealed tubulopapillary, epithelioid neoplastic proliferation. Immunohistochemical staining for the epithelial glycoprotein Ber-EP4 was negative, whereas results were positive for mesothelial markers, thus leading to the diagnosis of epithelial mesothelioma. The tumour infiltrated the testicular surface and the epididymis, but no distant metastases were found. The patient was treated with radical inguinal orchidectomy without adjuvant therapy and is free from disease 15 months after diagnosis. Tunical mesothelioma may simulate metastatic carcinoma at routine histopathological examination. Immunohistochemistry and occupational anamnesis are helpful for the correct diagnosis, which, in turn, is important for prognosis and treatment, and in relation to legal issues when asbestos is involved in the causation of the disease.