This study tests the effectiveness of parent-teen psychotherapy for adolescent attention-deficit/hyperactivity disorder (ADHD) (Supporting Teens' Autonomy Daily [STAND]) versus usual care (UC) in 4 community clinics. A randomized clinical trial was conducted with double randomization of adolescents and therapists to STAND versus UC. Participants were 278 culturally diverse adolescents diagnosed with DSM-5 ADHD at baseline and 82 community therapists. Seven primary outcomes were assessed at baseline (BL), posttreatment (PT; mean= 5.11 months post-BL, SD= 2.26), and follow-up (FU; mean= 9.81 months post-BL, SD= 2.50): inattention (IN; parent/teacher-rated), academics (parent-rated/official records), family functioning (parent/adolescent-rated), and disciplinary records. Treatment engagement indicated consumer fit (eg, number or sessions received, percentage of sessions attended by parent, satisfaction). The impact of treatment on concurrent medication use was also examined. Service delivery features were examined as moderators of outcome. Intent-to-treat (N = 278) analyses indicated no significant group× time effects. STAND only led to superior outcomes when therapists were licensed (22% of sample) versus unlicensed (parent-rated IN: p< .001, d= 1.08; parent-rated academic impairment: p= .010, d= 1.17). Compared to UC, STAND was associated with greater parent participation (p< .001, d= 0.88) and higher scores on certain indices of parent satisfaction. STAND also was associated with superior medication engagement over time compared to UC (odds ratio = 7.18). Evidence-based psychosocial treatment for adolescent ADHD did not outperform UC on outcome trajectories despite improving some indices of treatment engagement. STAND requires additional adaptation for community contexts. STAND Community Trial (STAND); https://clinicaltrials.gov/; NCT02694939.