A 54-year-old Chinese man presented with ascites for 2 weeks. He had a preceding 2-year history of intermittent dysphagia, lethargy and general malaise. Blood investigations revealed leucocytosis with eosinophilia of 26.5%, whereas paracentesis showed turbid fluid with high protein content (45 g/L) and a high white blood cell count of 5580/µL, predominantly eosinophils (90%). An incidental assay of vitamin D showed a very low level of 13.5 ng/mL. No other cause of ascites was found. Gastroscopy was normal except for duodenitis. However, biopsies from lower oesophagus confirmed the presence of eosinophilic infiltration. Following vitamin D replacement, the patient experienced marked improvement in symptoms of dysphagia within 2 weeks and no recurrence of ascites after 3 months. The reason for the patient's vitamin D deficiency remains unclear. The marked improvement in the patient's health indicates a causative role of vitamin D deficiency in causing eosinophilic esophagogastroenteritis and associated eosinophilic ascites.