Phaeochromocytoma is a rare cause of hypertension in children, but important to be recognised, as hypertension can be severe and surgery is often curative. Here, we report on a 7-year-old boy with a phaeochromocytoma, who had normal levels of commonly assayed catecholamine metabolites in the urine. Postoperatively, the patient developed renal vein thrombosis. Appropriate screening tests for phaeochromocytomas, peri-operative management, and the high incidence of an underlying genetic basis, even in sporadic cases, are discussed.