The presence of inappropriate sexual behaviors in individuals with autistic disorder is one of the important factors disturbing their social adaptation and distressing their families and environment. Therefore, appropriate management of these behaviors seems necessary. This case report describes a 13-year-old male with diagnosis of autistic disorder and fetishistic behavior. His fetishistic behavior was treated successfully using mirtazapine 15 mg/day. The clinical picture and efficacy of mirtazapine will be discussed.