<![CDATA[Character formation among adolescents in Islamic boarding schools (pesantren) is shaped not only by the formal educational environment but also by the social dynamics that occur among peers. This study examines the direct and indirect effects of pesantren education on santri character formation, with peer group as a mediating variable. A quantitative associative design was employed, involving 60 santri selected through purposive sampling. Data were collected using a validated and reliable five-point Likert-scale questionnaire (10 items per variable; Cronbach's alpha of .872, .831, and .810 for pesantren education, peer group, and character formation, respectively) and were analyzed through classical assumption tests, simple and multiple linear regression, and the Sobel test. The results show that pesantren education has a significant direct effect on peer group (β = .740; p < .001) and on character formation (β = .739; p < .001), and that peer group significantly affects character formation (β = .380; p = .003). The Sobel test confirms a significant indirect effect of pesantren education on character formation through peer group (z = 2.905; p = .004), indicating partial mediation, with the mediated pathway accounting for approximately 38% of the total effect. These findings suggest that pesantren education shapes santri character both directly, through habituation, exemplary role models, and a controlled environment, and indirectly, by cultivating a positive peer climate that reinforces religious and social values. The study offers practical implications for pesantren administrators to design peer-based character-reinforcement programs alongside formal educational activities.]]>
