There has been a significant increase in the development of interventions to improve the social competence and success of adolescents with autism spectrum disorder. The current investigation used direct observation and coding of social conversations as a rigorous method to further assess the efficacy of the Social Tools And Rules for Teens socialization intervention for adolescents with autism spectrum disorder in the context of a randomized controlled trial. A total of 35 adolescents with high-functioning autism spectrum disorder were randomized to either a treatment or waitlist control group. The 20-week group intervention took place once a week for 90 min per session. Brief video-recorded conversations between participants and unfamiliar, untrained peers were recorded at pre- and post-time points and coded for selected social behaviors (i.e. questions asked, positive facial expressions, and mutual engagement). Results revealed a significant Group × Time treatment effect for both questions asked and positive facial expressions. The findings support that the Social Tools And Rules for Teens intervention can positively impact specific, observable social behaviors through systematic coding of live social conversations within the context of a randomized controlled trial. This investigation is one of the first randomized controlled trials of a group socialization intervention to use systematic coding of live social conversations to assess social competence improvements.