Patients with juvenile systemic lupus erythematosus (JSLE) and juvenile dermatomyositis (JDM) are at higher risk of cardiovascular disease, with premature mortality. Adolescents and young adults with JSLE/JDM experience high rates of psychological stress which is associated with worse cardiovascular health (CVH) behaviors, including inadequate physical activity, diet quality, and sleep. However, evidence-based behavioral interventions for stress reduction remain inaccessible for many adolescents and young adults with JSLE/JDM. There is a critical need for stress reduction interventions that are effective, accessible, and tailored to JSLE/JDM-specific experiences. 'Teams Engaged in Accessible Mental Health Interventions for Lupus Erythematosus and Dermatomyositis Stress', or TEAM-LEADS, is an online stress reduction and CVH behavior promotion intervention for adolescents and young adults with JSLE/JDM. TEAM-LEADS will be evaluated in a Phase I open-label, single-arm successive cohort pilot trial in adolescents and young adults with JSLE and JDM. Participants will complete the online intervention and assessments at baseline, post-intervention, and follow-up. The study will evaluate feasibility, acceptability, adherence, and preliminary efficacy for stress reduction and CVH behavior promotion.