BACKGROUND Pseudomesotheliomatous carcinomas are rare tumors that develop like malignant pleural mesothelioma (MPM). These tumors have similar features, and thus pseudomesotheliomatous carcinomas can sometimes be misdiagnosed as MPM. Most pseudomesotheliomatous carcinomas develop from primary lung cancers, although there have been some reports involving other malignancies; however, there has been no report describing a pseudomesotheliomatous carcinoma developing from an esophageal squamous cell carcinoma (ESCC). To the best of our knowledge, this is the first case report describing pseudomesotheliomatous carcinoma originating from primary ESCC. CASE REPORT A 65-year-old man was admitted to our hospital because of persistent cough and right chest pain. Radiological examination suggested MPM, and a high concentration of pleural hyaluronic acid was also observed. Cytological examination of pleural effusion confirmed metastatic squamous cell carcinoma, and ESCC was confirmed by upper-gastrointestinal endoscopy. The patient received cisplatin and 5-FU combination chemotherapy as first-line treatment, and docetaxel chemotherapy as second-line treatment. However, the patient's condition deteriorated, and he died 6 months after the diagnosis was established. We performed an autopsy and found that ESCC had invaded the lung, pleura, peritoneum, liver, stomach, ureter, bladder, spine, and lymph nodes. CONCLUSIONS We demonstrated that primary ESCC can give rise to a pseudomesotheliomatous carcinoma. This report describes the clinical features and outcome of such a patient, with an emphasis on differential diagnosis of MPM.