Aim: Participation of adolescents with autism spectrum disorder hardly occurs in settings outside of home and school. Little is known about how their participation is influenced by environmental factors. This study explored how and why adolescents with autism spectrum disorder perceive aspects of their environment as facilitators or barriers to their participation outside of home and school.

Method: This explanatory case study explored the participation experiences of adolescents with autism spectrum disorder (15–21 years) from Zurich and surroundings with in-depth interviews and photo-elicitation, using photos made by the participants during activities outside of home and school. Data was analysed with a 7-step procedure.

Result: The presence of two main themes seemed necessary to facilitate participation outside of home and school: “environmental prerequisites to attend activities”, which consists of five subthemes, such as “the company of trusted persons” and “the provision of knowledge and information”, and “social interchange and engagement”, which consists of three subthemes and describes how actual involvement can be supported.

Conclusion: Our findings highlight the influence of trusted persons on adolescents with autism spectrum disorder, and the need to extend the support network for these adolescents to other individuals, services and society so that their participation in activities can be encouraged.