The main purpose of this research was to analyze school social workers’ core roles in serving autistic students in elementary and middle schools. An in-depth interview method was used in the study to collect data from five school social workers at Taipei City Student Counseling Center. The research results showed that the core roles of school social workers in serving autistic students, parents, and trans-professional partners included coordinators, educators, consultants, resource linkers, support companions, and advocators. Secondly, the school social workers played different roles in the micro, meso, and macro levels of an ecosystem and executed systematic cooperation for students with autism in primary and secondary schools. Finally, suggestions for future practice are as follows: (1) to master the core roles of school social workers and implement the three-level guidance system; (2) to strengthen trans-profession cooperation and implement role division and network cooperation. (3) to practice multi-roles under the ecosystem perspective.