Loneliness and social isolation are serious social issues that negatively affect the mental health of adolescents, and early interventions are crucial for prevention. This study evaluated preliminary changes in young people following their participation in the Education for Boosting Communication and Confidence for Healthy Independence (e-BOCCHI) program, a psychoeducational intervention designed to support the primary prevention of adolescent loneliness and social isolation. This program reframes loneliness and social isolation, teaches social skills, and encourages adolescents to seek help through role playing, group activities, and identifying meaningful solitary activities. Eighth-grade students ( N  = 324) from three middle schools in Japan were invited to participate, with 263 students (81.17%) completing the program and providing valid data for analysis. The participants completed questionnaires measuring loneliness, depressive symptoms, help-seeking behavior, and self-esteem before and after the program. The changes in scores were analyzed using paired t -tests. After adjustments for multiple comparisons, significant improvements were observed in depressive symptoms and help-seeking behavior; however, changes in loneliness and self-esteem were not statistically significant. These findings suggest that the e-BOCCHI program may strengthen certain protective factors and improve specific mental health outcomes among adolescents. This study was limited by the lack of a control group and reliance on short-term, within-sample comparisons, underscoring the need for randomized controlled trials to assess the program’s long-term effects and causal impact.