The purpose of this study was to examine the effects of an 8-week stress management intervention to enhance resilience and coping techniques and decrease stress in adolescent students. Teenagers, 11 to 17 years old, recruited from two tertiary Adolescent Medicine Centers of the National and Kapodistrian University of Athens, Greece, were randomly assigned into two groups: the stress management group (n=24) and the control group (n=25). Resilience, stress, anxiety, everyday use of social media, school performance and cognitive skills were measured in adolescents of both groups, pre- and post-intervention. Post-intervention, the stress management group had significantly higher resilience scores and school performance self-evaluation scores, lower scores of stress, anxiety and everyday use of social media and better cognitive skills than the control group. Regarding cognitive skills, the stress management group significantly improved the speed of information processing and memory. Adolescents following stress management experienced significantly reduced stress from interacting with teachers/parents, from peer pressure, from school/leisure conflict as well as compulsive behaviours. With respect to resilience, the intervention improved adolescents' individual skills and resources, relationships with primary caregivers, and environmental factors that facilitated the sense of belonging. Future studies of large adolescent samples are required to evaluate the long-term benefits of stress management techniques on adolescents' health and resilience, as well as the need of continued support to preserve these benefits throughout transition to adulthood.