Cyberbullying is a growing public health concern for adolescent mental well-being worldwide. School-based programs are widespread, yet many prioritize behavioral deterrence over the psychosocial mechanisms (coping, emotion regulation, help-seeking) through which harm may be reduced. This systematic review, reported in accordance with PRISMA 2020, synthesizes recent Scopus-indexed evidence (2015–2026) on school-based psychological interventions for cyberbullying prevention and adolescent mental well-being. A title-field search retrieved 218 records. After removal of records before screening, title/abstract screening, full-text retrieval, and eligibility assessment, five peer-reviewed articles (two meta-analyses, one pilot trial, one cross-sectional survey, and one narrative review) were retained and synthesized thematically. Three themes emerged. (1) Meta-analytic evidence suggests that multicomponent programs combining cognitive-behavioral techniques (CBT), social-emotional learning (SEL), and empathy training are associated with reductions in cyber-perpetration and cyber-victimization, although the durability of effects remains uncertain. (2) A single pilot study suggests that an online, self-guided CBT-based module may strengthen adolescents’ confidence in handling cyberbullying and their willingness to seek help; evidence on mental-health outcomes is still preliminary. (3) Family and cultural context, including parental stress, digital mediation styles, and stigma surrounding counseling, appears to condition implementation, particularly in the Vietnamese context. Because the evidence base is small, heterogeneous in design, and rarely reports mental-health outcomes directly, conclusions are tentative. The review offers a research agenda and preliminary implications for educational psychologists and policymakers designing school-based mental health support.