This study identifies behaviours that support self-understanding for people with autism spectrum disorder (ASD) participating in vocational rehabilitation. The qualitative research (Study 1) used conceptual analysis to identify vocational rehabilitation practitioners’ concept of support for self-understanding. The quantitative research (Study 2) surveyed 155 Japanese vocational rehabilitation practitioners using a questionnaire based on the results of Study 1. Exploratory factor analysis of the survey data determined the structure of behaviours that support self-understanding for people with ASD and found three behaviour types: ‘Environmental setting of the current situation’, ‘Promoting awareness of the current situation’, and ‘Reflection based on collected information’. A practitioner was deemed to promote self-understanding support by using a combination of these three behaviours while heeding to the disabling characteristics of people with ASD. Identified support behaviours could be used as a fundamental perspective to develop a support programme to promote self-understanding for people with ASD.