Hydroxychloroquine is an antimalarial drug, which is also used for the treatment of rheumatoid arthritis, lupus erythematosus (both systemic and discoid), Sjögren Syndrome, post-Lyme arthritis, and chronic Q fever. Although antimalarial drugs have been associated with various side effects including neuropsychiatric symptoms such as depression, claustrophobia, feelings of inferiority, increased dreaming, loss of sleep from noxious dreams, suspiciousness, loss of affection, labile affect, delirium, delusions, auditory hallucinations and visual hallucinations; psychosis induced by hydroxychloroquine is unexpected. A 51-year-old, married female patient suffering from insomnia for 4 days was admitted to psychiatry outpatient clinic. She had auditory hallucinations, perspective and reference delusions, impairment in judgment for twenty days. Since nine years, she has usedseveral drugs such as methotrexate, salicylazosulphapyridine, prednisolone, and adalimumab because of a diagnosis of rheumatoid arthritis. Four months ago, hydroxychloroquine 200 mg/day (d) was added to her treatment for her shoulder pain. The brain MRI and the results of all laboratory tests were normal. At admission, Scale for the Assessment of Positive Symptoms (SAPS) and Scale for the Assessment of Negative Symptoms (SANS) scores were 18 and 0, respectively. For her insomnia and the prominent psychotic symptoms, quetiapine was started at a dose of 25 mg/d and titrated up to 75 mg/d. One week later quetiapine was changed to olanzapine 5 mg/d because of tachycardia. Within one month, the dose of olanzapine was increased to 20 mg/d. Also, haloperidol 1 mg/d and alprazolam 0,5 mg/d were added to treatment for her positive symptoms of psychosis. Initially, the drugs which the patient received for rheumatoid arthritis were not discontinued and we tried to manage psychiatric symptoms with antipsychotic treatment. When we noticed her psychotic symptoms were persisting despite an effective antipsychotic treatment, we decided to discontinue hydroxychloroquine, as we predicted insomnia and psychotic symptoms developed one-two months after hydroxychloroquine was added on previous drugs. One week later hydroxychloroquine was stopped, her primary psychotic symptoms resolved (SAPS=2, SANS=0). Therefore, we supposed that the psychotic symptoms of this patient might be related to short-term hydroxychloroquine treatment. Then, we discontinued the all-antipsychotic drugs, and observed that her primary psychotic symptoms did not relapse until now. The exact mechanism psychosis associated with hydroxychloroquine or chloroquineis not clear but these mechanisms are suggested to be related with dopaminergic and anticholinergic effects. It was shown in an animal study that, usage of chloroquine, in low doses, produced excitatory effects. Chloroquine might increase dopaminergic activity by increasing dopamine-transporter protein turnover and decreasing the down regulation of post-synaptic dopamine receptors. The anticholinergic effects of chloroquine in cortex contribute to the neuronal mediation of psychotic symptoms by affecting mesolimbic dopaminergic transmission. Das et al. suggested another one that hydroxychloroquine might cause a lysosomal dysfunction by accumulation in lysosomes of cells which could be probable for psychotic symptoms. In light of this and previous cases in the literature, relationship between hydroxychloroquine and psychosis should be considered. Our case indicates that long-term antipsychotic drug interventions might not be necessary in such patients developed psychotic symptoms following hydroxychloroquine treatment.