The inclusion of students with autism spectrum disorder (ASD) is increasing, but there have been no longitudinal studies of included students in Australia. Interview data reported in this study concern primary school children with ASD enrolled in mainstream classes in South Australia and New South Wales, Australia. In order to examine perceived facilitators and barriers to inclusion, parents, teachers, and principals were asked to comment on the facilitators and barriers to inclusion relevant to each child. Data are reported about 60 students, comprising a total of 305 parent interviews, 208 teacher interviews, and 227 principal interviews collected at 6-monthly intervals over 3.5 years. The most commonly mentioned facilitator was teacher practices. The most commonly mentioned barrier was intrinsic student factors. Other factors not directly controllable by school staff, such as resource limitations, were also commonly identified by principals and teachers. Parents were more likely to mention school- or teacher-related barriers. Many of the current findings were consistent with previous studies but some differences were noted, including limited reporting of sensory issues and bullying as barriers. There was little change in the pattern of facilitators and barriers identified by respondents over time. A number of implications for practice and directions for future research are discussed.