Objective: Tardive dyskinesia (TD) is an iatrogenic movement disorder, developing due to prolonged use of dopamine receptor blocking agents, that may affect various parts of the body. In a number of studies, prevalence rates between 5 and 30% have been reported. This study aims to research TD in patients with mental retardation who have been hospitalized for a long time and medicated regularly. Method: Included in this study were 40 patients with a diagnosis of mental retardation comorbid with schzophrenia or other psychotic disorders according to DSM-IV TR that had been hospitalized in the chronic patients’ ward of Bakirkoy Training and Research Hospital for Psychiatry, Neurology and Neurosurgery for a long period. Duration and type of antipsychotics both at the time of interview and over the preceding years were recorded. Dyskinesia was assessed using the Abnormal Involuntary Movements Scale (AIMS). We also used the Simpson–Angus Rating Scale (SAS) for Parkinsonism. Akathisia was measured using the Barnes Akathisia Rating Scale (BARS). Results: According to AIMS scores, 9 participants (22.5%) received a diagnosis of TD. There was no significant correlation between the type and duration of ongoing or the longest used treatment and the prevalence of TD. There was a statistically significant correlation between the participants’ age and TD (p=0.009). There were no gender differences for TD Conclusion: We found that long-term use of antipsychotics is unrelated with TD, while age is an important risk factor for TD. It can be said that switching from first generation to second generation antipsychotics does not reduce the prevalence of TD.