The aim of the present study was to investigate the influence of self-awareness of real-world behavior on treatment outcome in adolescents with ASD. For this purpose we followed 28 adolescents with ASD during their first year of specialized treatment. Results showed that better self-awareness at start of treatment was related with an increase in clinician-reported social functioning after 1 year of treatment. Additionally, an increase in self-awareness during treatment was related with a decrease of parent-reported problems in daily functioning. However, an increase in self-awareness was also related to an increase of self-reported daily and psychological problems. It is discussed that lowered self-awareness may result in an overestimation of personal real-world functioning and consequently may influence treatment course.