en تخصصي Special پژوهشي Research Objective: Fragile X syndrome is the second etiology for inherited mental retardation. It may concomitant with other psychiatric disorders. Intellectual disability (ID) is a state of functioning that typically begins in childhood and is characterized by limitations in intelligence and adaptive skills. We intend to introduce a male young patient with Fragile X syndrome and Obsessive-Compulsive disorder. Case Presentation: A single, obese male patient with aggressive behaviors, intellectual disabilities, hyperphagia and Obsessive–Compulsive disorder was admitted for treatment. Behavioral problems and impaired interpersonal relationship was caused many of next problems. Also metabolic syndrome is suggested for him. Conclusion: In a mental retard patient, obsession may not be a chief complaint, but we saw compulsive behavior dominantly in this patient. Some cultural factors like stigma, low social support and unsuitable community approach towards him may be effective in this case. So, further evaluations and treatment of psychiatric and medical co morbidities is highly needed in an adolescent with mental retardation. Fragile X syndrome, Hyperphagia, Mental retardation, Obsessive-compulsive disorder 182 185 http://ijdo.ssu.ac.ir/browse.php?a_code=A-10-30-93&slc_lang=en&sid=1 Seyed-Ali Mostafavi No PhD Candidate, Psychiatry Research Center, Roozbeh Hospital, Tehran University of Medical Sciences, Tehran, Iran. Pouria Yazdian-Anari No Yazd Student Research Committee, Shahid Sadoughi University of Medical Science, Yazd, Iran. Maryam Mahmoudi No Medical Student. Rafsanjan University of Medical Sciences, Rafsanjan, Iran. Fahimeh Mirzaei No Medical Student. Rafsanjan University of Medical Sciences, Rafsanjan, Iran. Reza Bidaki Yes MD. Assistant Professor of Psychiatry. Department of Psychiatry, Research Center of Addiction and Behavioral Sciences, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Mohammad Hossein Mahmoodi Meymand No Medical Student. Rafsanjan University of Medical Sciences , Rafsanjan, Iran.