A 15-month-old boy with a 2-month history of watery diarrhoea presented with cachexia, hypokalaemia, hypochloraemia and metabolic acidosis. During a 2-week investigation period infection, celiac disease and cystic fibrosis were excluded and trial therapy with antibiotics, probiotics and dietary measures proved unsuccessful. This led to the suspected diagnosis of a vasoactive intestinal polypeptide (VIP)-secreting tumour with watery diarrhoea, hypokalaemia, achlorhydria (WDHA)-syndrome. MRI showed an infrarenal mass infiltrating the neuroforamen, which on pathological examination was consistent with a VIP-secreting neuroganglioblastoma. Serum VIP and urinary catecholamine levels were elevated. Treatment consisted of 2 courses of chemotherapy and a partial resection of the tumour, following which the diarrhoea disappeared. Refractory watery diarrhoea that persists during fasting in a young child should alert to the diagnosis of WDHA, and prompt investigations to diagnose a VIP-secreting tumour, one of the most common causes of secretory diarrhoea in the developed world. Timely diagnosis could avoid morbidity due to unnecessary investigations and protracted diarrhoea.