Coronavirus disease 2019 (COVID-19) can affect multiple organs and systems, including the endocrine system. Its symptoms can last for months, resulting in post-COVID-19 conditions, among others. A small number of patients have central adrenal insufficiency (CAI) months after recovery from COVID-19; nevertheless, its pathogenesis has not been fully elucidated. The insulin tolerance test (ITT) is a gold standard test assessing the hypothalamic-pituitary-adrenal axis, and the corticotropin-releasing hormone (CRH) test is useful for differentiating CAI into secondary (pituitary) and tertiary (hypothalamic) adrenal insufficiency. We present a case of new-onset CAI in a young female patient who had no medical history other than COVID-19. Adrenocorticotropin hormone and cortisol responded poorly to both insulin-induced hypoglycemia and CRH administration. These findings suggest that the pituitary gland may be the primary site of hypothalamic-pituitary-adrenal dysfunction, although magnetic resonance imaging of the pituitary gland was unremarkable. To our knowledge, this is possibly the first and only case report of new-onset secondary adrenal insufficiency after recovery from COVID-19 in which the ITT and the CRH test were performed and highly suggestive for the pathogenesis of not only post-COVID-19 CAI but also post-COVID-19 conditions.