A six-session higher-functioning autism anti-stigma program incorporating descriptive, explanatory and directive information was delivered to adolescent boys and the impact upon knowledge, attitudes and behavioural intentions towards peers with autism was evaluated. Participants were seventh-, eighth- and ninth-grade students (N = 395) from regular classes in a mainstream school. Two-eighth-grade classes were randomly allocated to the intervention condition and all remaining students were either allocated to the no-intervention peer or no-intervention non-peer condition. The anti-stigma program improved the knowledge and attitudes, but not the behavioural intentions of participants towards their peers with autism. Knowledge and attitudinal changes were maintained at follow-up. There were no spill-over effects of the program to non-targeted students. These results provide some preliminary evidence for the effectiveness of multi-session anti-stigma programs incorporating combined information for adolescent students in inclusive educational environments.