Background. Catatonia is a complex neuropsychiatric disorder involving stupor, waxy flexibility, and mutism lasting more than 1 hour. It has arisen mostly from mental and neurologic disorders. Organic causes are more prominent in children. Case. A 15-year-old female who had refused to eat and drink for 3 days, had not talked, and had stood in a fixed position for long periods was admitted to the inpatient clinic, and she was diagnosed with catatonia. Her maximum score on the Bush-Francis Catatonia Rating Scale (BFCRS) was 15/69 on day 2 of her stay. On neurologic examination, the patient`s cooperation was limited, and she was apathetic to her surroundings and stimuli and inactive. Other neurologic examination findings were normal. To investigate catatonia etiology, her biochemical parameters, thyroid hormone panel, and toxicology screening were conducted but all parameters were normal. Cerebrospinal fluid examination and autoimmune antibodies were negative. Sleep electroencephalography showed diffuse slow background activity, and brain magnetic resonance imaging was normal. As a first-line treatment for catatonia, diazepam was started. With her poor response to diazepam, we continued to evaluate the cause and found the transglutaminase levels were 153 U/mL (normal values, <10 U/mL). The patient`s duodenal biopsies showed changes consistent with Celiac disease (CD). Catatonic symptoms did not benefit from a gluten-free diet or oral diazepam for 3 weeks. Then, diazepam was replaced with amantadine. With amantadine, the patient recovered within 48 hours, and her BFCRS retreated to 8/69. Conclusions. Even without gastrointestinal manifestations, CD may present with neuropsychiatric symptoms. According to this case report, CD should be investigated in patients with unexplained catatonia, and that CD may only present with neuropsychiatric symptoms.