Non-thyroidal illness syndrome (NTIS), a remarkable ensemble of changes in serum thyroid hormone concentration during acute illness, was first reported in the 1970s. While NTIS is not a form of hypothyroidism, it is characterized by a decrease in serum triiodothyronine (T3) or thyroxine (T4) or both with normal or decreased thyroid-stimulating hormone (TSH). Notably, it typically resolves without thyroid hormone replacement therapy. We report a case of paralytic ileus caused by NTIS in an infant with psychological stress. This case illustrates the development of NTIS during psychological stress, which can lead to severe symptoms such as those seen in pathological hypothyroidism.