Adolescents with Internet addiction (IA) frequently encounter elevated levels of anxiety and depression, which subsequently results in the perpetuation of their addiction behaviors. Mindfulness-based cognitive therapy for children (MBCT-C) is an adapted version of traditional MBCT that targets emotional problems in children. The present study aimed to provide a framework for the implementation of a clinical trial for its effectiveness in reducing anxiety, depression, and IA in adolescents with IA. This study protocol proposes a randomized controlled trial with two parallel arms (MBCT-C versus active control). Eighty Iranian adolescents (Persian ethnicity; males and females; 12 to 15 years) diagnosed with IA will be randomly assigned to the intervention group (12 sessions of MBCT-C group therapy) or the control group (12 life skills training sessions). Pre-intervention, post-intervention, and three-month follow-up assessments will be conducted using Mindful Attention Awareness Scale-Adolescents (MAAS-A), Mindfulness Program Satisfaction Questioner (MPSQ), Reynolds Adolescent Depression Scale (RADS), State-Trait Anxiety Inventory-Children (STAI-C), MBCT-C Adherence Scale (MBCT-C-AS), and Internet Addiction Test (IAT). Data will be analyzed using mixed regression model using STATA-18 to assess the effectiveness of MBCT-C. The current study has the potential to make a significant contribution to evaluate the effectiveness of MBCT-C to address IA, anxiety, and depression in adolescents with IA.