Ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS) is rarely caused by a phaeochromocytoma. We report a case of a 51-year-old woman with an 8-year history of severe constipation who underwent extensive investigations including gastroscopy, colonoscopy, ultrasonography, colonic transit studies and isotope defeacography, which did not reveal any pathology other than slow colonic transit time. The unifying diagnosis of ectopic ACTH and phaeochromocytoma was made after the case was initially investigated for an adrenal incidentaloma. Multiple challenges had to be overcome prior to surgery for the functioning adrenal adenoma including management of refractory hypokalaemia, poor nutritional status, persistent hyperglycaemia, labile blood pressure and florid hypercortisolaemia driving the metabolic derangements. She underwent an uneventful left-sided adrenalectomy and required no medication thereafter with normal blood pressure, blood glucose and serum potassium and resolution of constipation and abdominal symptoms. In conclusion, patients with EAS related to phaeochromocytoma are rare and present with distinctive diagnostic and management challenges but if diagnosed successfully and managed intensively, they are curable.