Adolescents with autism spectrum disorder (ASD) are vulnerable to declines in social connections and an increase in depression, anxiety, and other co-occurring conditions. This study introduces a novel intervention that matches adolescents and adults with ASD in one-to-one mentoring relationships in an afterschool setting and examines its social validity. In this single-group, mixed-method pilot study, participants were seven adolescent mentees (14-18 years old; 100% male), seven adult mentors (19-33 years old; 71% male), and eight parents of mentees. A combination of project-specific and standardized assessments was used to describe the participants' perceptions of the program and to assess well-being, self-concept, and social-emotional and behavioral outcomes. Results showed high uptake, program satisfaction, positive ratings of mentoring relationship quality, and desirable pre- to post-test change on several targeted outcomes. This study provides preliminary evidence to support the applicability and utility of a mentoring program for adolescents with ASD by adults with ASD.