Ectopic ACTH syndrome (EAS) is rare but is frequently a severe condition because of the intensity of the hypercortisolism that may be dissociated from the tumoral condition. EAS should often be considered as an endocrine emergency requiring an emergency response both in terms of diagnostic procedures and therapeutic interventions. Patient management is complex and necessitates dual skills, in the diagnosis and treatment of CS and in the specific management of neuroendocrine tumors (NET). Therefore, initial management should be performed ideally by experienced endocrinology teams in collaboration with specialized hormonal laboratory, modern imaging platforms and intensive care units. Diagnostic procedures vary according to the endocrine and tumoral contexts but should be reduced to a minimum in intense hypercortisolism. Preventive and curative treatments of cortisol-induced comorbidities, non-specific management of hypercortisolism and etiological treatments should be considered simultaneously. Therapeutic strategies vary according to (1.) the intensity of hypercortisolism, the general condition of the patient and associated comorbidities and (2.) the tumoral status, ranging from resectable ACTH secreting tumors to non-resectable metastatic endocrine tumors or occult tumors. The ideal treatment is complete excision of the ACTH-secreting tumor that can be performed rapidly or after preoperative preparation using cortisol-lowering drugs. When this is not possible, the therapeutic strategy should be discussed by a multidisciplinary experienced team in a personalized perspective and include variable combinations of pharmacological agents, bilateral adrenalectomy and non-specific tumoral interventions. Here we discuss the diagnosis and therapeutic strategies including the modern, currently available tools and emphasize on the operational effectiveness of care.