Objectives: Among the many intervention programs for children with autism spectrum disorder (ASD), the Early Start Denver Model (ESDM) is one of the few approaches that has succeeded in demonstrating clinical efficacy in randomized control trials. Here, we investigate the clinical efficacy of ESDM intervention in young children with ASD in a community setting within Japan. Methods: All subjects were children with ASD who received ESDM intervention during the study period. Each ESDM session lasted 75 min and occurred once per week for at least 12 weeks. The outcome measures consisted of the Kyoto Scale of Psychological Development (K-test), Aberrant Behavior Checklist-Japanese version (ABC-J), and the Clinical Global Impression-Severity scale (CGI-S). Results: Twenty-seven subjects (29.4±6.4 months old) received ESDM intervention that lasted for 8.0±2.6 months on average. The score on Language and Social developmental quotient on the K-test increased significantly after the intervention. The total scores on the ABC-J and CGI-S significantly decreased after completion of the ESDM intervention. Conclusion:Our results suggest that ESDM intervention could reduce the severity of distinct clinical features of ASD, such as impairments in social interaction and communication assessed by the K-test, and maladaptive behavior rated by the ABC-J and CGI-S. We believe that the ESDM adapted to each institution might become one of the standard options for children with ASD in Japan.