Background Managing Type 1 diabetes (T1D) during adolescence can be challenging, and there is a need for accessible interventions to help adolescents cope with diabetes-related stress. Objectives The aim of this study was to compare an Internet coping skills training (TEENCOPE) intervention to an Internet educational intervention (Managing Diabetes) for adolescents with T1D. Moderators of program efficacy were evaluated. Methods The study was a multisite clinical trial (n = 320) with data collected at baseline, 3 months, and 6 months. Data were collected on the primary outcomes of physiologic (A1C) and psychosocial (quality of life) and on the secondary outcomes of behavioral (self-management) and psychosocial (stress, coping self-efficacy, social competence, family conflict) variables consistent with the conceptual framework. Data were analyzed using mixed-model analyses with an intent-to-treat approach. Results There were no significant between-group treatment effects 6 months postintervention on primary outcomes. The Managing Diabetes youth showed a significant increase in social competence compared to the TEENCOPE youth. There were significant time effects for TEENCOPE (decreased stress and increased coping) and Managing Diabetes (improved diabetes quality of life). Discussion Youth with T1D transitioning to adolescence may need both structured diabetes education and coping skills to improve health outcomes. There may be a higher potential to reach adolescents with Type 1 diabetes of varying race and ethnicity via Internet interventions.