Mercury (Hg) poisoning is an uncommon but life-threatening condition and may cause serious complications. Acute mercury poisoning might cause a psychiatric picture with irritability, emotional instability, anxiety, depression, temper tantrums and psychotic symptoms. This paper presents a mercury poisoning case in a 14-years-old female with prominent psychiatric manifestations. Relevant literature concerning the psychiatric manifestations of mercury poisoning is discussed. A 14-year-old female patient is an 8th grade student living with her mother, father and siblings. She had played with mercury with her friends at school and swallowed two bead-sized mercury pieces. She was taken to hospital 1 day later with complaints of fatigue, weakness, nausea, dizziness and rush on her face. Common muscle pain and dilated pupils were observed as a result of her examination that was conducted by the Child Neurology. The maximum mercury level of the patient was measured as 8.9 microgram/L in urine of 24 hours. Metalcaptase treatment was administered on the patient. Her brain MR and EEG examinations were normal. She was discharged after a treatment of 14 days. Since she had visual field defect and psychiatric complaints during her polyclinic follow-ups, she was consulted to the Child Psychiatry. She was taken to the child psychiatry polyclinic with complaints of “dysmnesia and feeling like in a dream”. After her discharge, she began thinking that her parents were different; their house and furniture were all changed. She felt like the world and people were not real, she was not actually alive and this all was a dream. She occasionally could not recognize herself in the mirror and thought that her face and hands were different and then she started to forget things like her memories. When talking about them, she thought that she was lying since they had never really happened in her opinion. She occasionally daydreamed without thinking about anything and once she regained consciousness, she felt like she was in some other place. She had the depressive symptoms such as unhappiness, displeasure out of life and thoughts of worthlessness for more than one month. Her mother stated that she was more irritable and aggressive compared to past. During the psychiatric examination of the case who had no feature in her background, it was observed that her mood was depressive and she had depersonalization and derealization as a perceptual deficit. During the psychometric assessment, we determined the kovacs depression inventory as 28 (pathological), state anxiety (STAI-I) as 56 (pathological), trait anxiety (STAI-II) as 58 (pathological) and Dissociation scale as 2.73 (pathological). Following starting 50 mg Sertraline, the patient was followed up. During her examination 20 days later, her symptoms decreased but were still continuing. The patient did not appear in next follow-ups. Mercury poisoning, although relatively rare, is still a concern for the psychiatrists. Acute mercury poisoning could be accompanied by psychotic symptoms, delirium, hallucinations, and suicidal tendencies. Dissociative symptoms, anxiety, depression and irritability were observed in our case that was exposed to mercury through skin, by inhalation and orally.