Objective: This article reported the treatment process for a preschooler with Asperger's Disorder using cognitivebehavioral therapy (CBT). Method: A 5-year-old girl with Asperger's Disorder received nine sessions of CBT over the course of three months to alleviate her maladaptive symptoms. Each weekly session lasted for an hour. Two clinical psychologists were her therapists and parents were trained to be co-therapists. Results: The details of the 9 sessions' assessments and treatments were described. The evaluations showed a significant improvement in her sibling rivalry, and decrease in mood and sleep problems. Follow-up assessment at three months after termination revealed that improvement had been maintained. Conclusion: This case study illustrated that CBT, particularly applying verbal mediation to reach cognitive change, can be successfully used to treat or to prevent emotional/ behavioral problems of a preschool child with Asperger's Disorder.