Gastroparesis is a common but challenging disorder which can be idiopathic or induced by a variety of underlying diseases, most frequently by diabetes, or post-surgical conditions of the upper abdomen. Clinicians must also consider rare causes of gastric motor dysfunction, such as collagen vascular disorders and paraneoplastic syndromes. Here we present the case of a patient with severe gastroparesis, who was admitted to our hospital for vomiting and weight loss of 25 kg within four months. Endoscopy showed a dilated fluid-filled stomach without peristalsis but no obstruction. High titres of anti-Hu antibodies were detected in patient's serum, supporting the diagnosis of severe paraneoplastic gastroparesis with chronic intestinal pseudo-obstruction. Fine-needle aspiration of suspicious mediastinal lymph nodes guided by endoscopic ultrasound revealed lymphatic metastases of a small-cell lung carcinoma. Jejunal tube feeding and chemotherapy with carboplatin and etoposide were initiated. Paraneoplastic gastrointestinal dysmotility is rare, however, clinicians should consider this differential diagnosis in otherwise unexplained gastrointestinal motor dysfunction. The pathophysiology of paraneoplastic gastroparesis, the diagnostic relevance of anti-Hu antibodies as well as therapeutic options are discussed.