Introduction: Landau-Kleffner syndrome (LKS), a very rare childhood disease, is acquired aphasia associated with epileptiform activity on the electroencephalogram (EEG). The clinical presentation of LKS may resemble autistic disorders in some children. In this article, a case who came to the Child and Adolescent Psychiatry outpatient clinic with autism symptoms but was diagnosed with LKS as a result of neurological examinations, showed significant improvement in autism symptoms after treatment is presented. Case: The boy aged 4 years 7 months was brought to the Child and Adolescent Psychiatry outpatient clinic with complaints of language regression, decreased interest in the environment, and impaired communication with peers and adults. After the neurological evaluations, the patient was diagnosed with LKS and antiepileptic treatment was started. An substantial improvement in language and social skills was observed within 1-3 months after adding corticosteroid therapy to the patient who did not benefit from antiepileptic treatment. Discussion: In this article, in cases where EEG pathology and autism symptoms did not improve with antiepileptic treatment in LKS; It has been reported that rapid improvement can be achieved in both neurological and autism symptoms after corticosteroid addition treatment. Although there is more information in the literature that known treatments are effective in improvement language regression in LKS, there are few case reports on reducing the accompanying autism symptoms.