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SUMMARY Long COVID is defined by the occurrence of signs, symptoms, and conditions that develop after COVID-19 and may affect several organs and systems. Arginine-vasopressin deficiency (AVP-D; central diabetes insipidus) is a very rare complication of COVID-19 and SARS-CoV-2 immunization. Case reports, original studies, and reviews on AVP-D and long COVID published until February 2024 were retrieved from PubMed. A 47-year-old man presented with polydipsia, polyuria, memory loss, and mental fog 8 weeks after an episode of mild COVID-19. His past personal and family medical history were unremarkable. Biochemical evaluation was relevant for low urine osmolality and a 24-hour urine volume of 10,350 mL. Basal anterior pituitary evaluation was normal. A water deprivation test was started and interrupted after 2 hours due to the development of hypernatremia, high serum osmolality, and low urine osmolality. Urine osmolality significantly increased after intranasal desmopressin 20 μg. Contrast-enhanced pituitary MRI was suggestive of infundibulo-neurohypophysitis. Further biochemical, genetic, and imaging tests excluded secondary AVP-D causes. The patient was subsequently started on oral desmopressin, showing prompt response. After a follow-up of 20 months, he remained well-controlled with isolated AVP-D. Although molecular and histologic confirmation of SARS-CoV-2 infundibulo-neurohypophysitis could not be investigated, a strong temporal relationship and the absence of an alternative diagnosis rendered plausible the inclusion of AVP-D in the myriad of long COVID manifestations. Further studies with patients recovered from COVID-19 are necessary for a better understanding of the epidemiology, pathophysiology, and clinical course of this very rare endocrine condition.