Background: The prevalence of chronic and complex pediatric health conditions has quickly risen over the last decades. Chronic and complex health conditions make pediatric patients and their families more susceptible to many distressing events during their lifespan. Mindfulness-based interventions have become a popular intervention for individuals living with chronic illnesses and have been adapted for pediatric populations with good results, including online versions. This study intends to report an implementation protocol of an online mindfulness-based program for adolescents to address an important gap in stress relief and health promotion for pediatric patients., Methods: In this article, we describe the rationale and design of an implementation study of an online mindfulness-based program for pediatric patients at a tertiary pediatric hospital in South America. Participants will be recruited during one year to participate in an eight-session online mindfulness-based program. To assess our primary aim of feasibility, we will exam recruitment, retention and participation rates. Participants will also complete a symptomatology evaluation (i.e., depression, anxiety, and stress symptoms) at baseline and immediately at post-treatment and fidelity will be evaluated by a structured questionnaire., Discussion: This study will be the first known to assess the implementation of an online mindfulness-based program for a pediatric population at a tertiary pediatric center in South America under real-life conditions. This study will establish the feasibility of a novel intervention aimed at promoting mental health and positive coping strategies among pediatric patients with chronic and complex health conditions. Evidence from this study would be useful to patients, families, clinicians, and policymakers and will help to devise strategies of health promotion for the pediatric population, as well as serve as a model for a future trial to examine efficacy of the proposed intervention., Trial Registration: This research has been registered at Ensaiosclinicos.gov.br , identifier RBR-23trp87 . Registered 25 February 2022-retrospectively registered., (© 2022. The Author(s).)