Churg-Strauss syndrome (CSS) is rarely presented as paraneoplastic syndrome. We reported here a 47-year-old man with refractory asthma for 3 years, and his CT scan showed an anterior mediastinal mass, pulmonary reticular opacities and bilateral maxillary sinusitis. He also presented with elevated peripheral blood eosinophils (EOS). Thoracoscopic resection of the mediastinal mass and a lung biopsy were performed, and thymic neuroendocrine carcinoma (TNC) and pulmonary eosinophilic vasculitis were pathologically diagnosed. The laboratory and clinical findings fulfilled the criteria of the diagnosis of CSS (Masi et al. in Arthritis Rheum 33(8):1094-1100, 1990). Asthma was improved, and elevated EOS was recovered to normal range after surgery and four courses of chemotherapy. This was the first report of CSS manifested as a paraneoplastic syndrome of TNC.