A 53-years-old woman with bilateral untreated breast cancer is admitted for intractable vomiting. No obstructive gastric disease is found but a marked delayed gastric emptying, suggesting the diagnosis of gastroparesis. No classical cause being demonstrated, the diagnosis of paraneoplastic gastroparesis is proposed. Treatment with cisapride and chemotherapy lead to regression of digestive symptoms and of breast tumor. This uncommon entity, usually described in association with small cell lung cancer, may involve the whole gastrointestinal tract, sometimes in association with abnormalities of the autonomous nervous system. Destruction of the myenteric plexuses by auto-antibodies could be responsible for this pathology.